Formally define existing assignment of responsibilities.

Author: whitequark

README.md

@@ -7,6 +7,15 @@ Many changes, including bug fixes and documentation improvements can be implemen
 
 Some changes though are "substantial", and we ask that these be put through a bit of a design process and produce a consensus among the Amaranth community.
 
+The responsibility for evolving an Amaranth "subsystem" (a clearly defined part of the Amaranth project) lies on a subsystem maintainer. The assignment of maintainers to subsystems is:
+- **Core**: Catherine @whitequark
+  - The "core" subsystem includes the HDL frontend, backend, and simulator, as well as the build and platform systems.
+  - This covers the [amaranth-lang/amaranth][] repository and the `amaranth` Python package.
+- **SoC**: Jean-François @jfng
+  - The "SoC" subsystem includes the SoC infrastructure.
+  - This covers the [amaranth-lang/amaranth-soc][] repository and the `amaranth_soc` Python package.
+- Other repositories and Python packages are not currently covered by the RFC process and changes are implemented on an ad-hoc basis.
+
 ## Table of Contents
 [Table of Contents]: #table-of-contents
 
@@ -24,7 +33,7 @@ Some changes though are "substantial", and we ask that these be put through a bi
 ## When you need to follow this process
 [When you need to follow this process]: #when-you-need-to-follow-this-process
 
-You need to follow this process if you intend to make "substantial" changes to [core Amaranth language][amaranth]. In the future you will need to follow this process for the [standard I/O library][amaranth-stdio] and the [System-on-Chip library][amaranth-soc] as well, but at the moment they are not covered.
+You need to follow this process if you intend to make "substantial" changes to any of the subsystems listed above.
 
 What constitutes a "substantial" change is evolving based on community norms and varies depending on what part of the ecosystem you are proposing to change, but may include the following:
 
@@ -37,7 +46,7 @@ Some changes do not require an RFC:
 - Rephrasing, reorganizing, refactoring, or otherwise "changing shape does not change meaning".
 - Additions that strictly improve objective, numerical quality criteria (warning removal, speedup, better platform coverage, handling more errors, etc.)
 
-If you submit a pull request to implement a new feature without going through the RFC process, it may be closed with a polite request to submit an RFC first. When in doubt, please open an issue to discuss the feature first and one of the core maintainers will say if the change requires an RFC or not.
+If you submit a pull request to implement a new feature without going through the RFC process, it may be closed with a polite request to submit an RFC first. When in doubt, please open an issue to discuss the feature first and the subsystem maintainer will say if the change requires an RFC or not.
 
 [amaranth]: https://github.com/amaranth-lang/amaranth
 [amaranth-stdio]: https://github.com/amaranth-lang/amaranth-stdio
@@ -64,8 +73,8 @@ In short, to get a major feature added to Amaranth, one must first get the RFC m
 - Now that your RFC has an open pull request, use the issue number of the PR to update your 0000- prefix to that number.
 - Build consensus and integrate feedback. RFCs that have broad support are much more likely to make progress than those that don't receive any comments. Feel free to reach out to the RFC assignee in particular to get help identifying stakeholders and obstacles.
 - RFCs rarely go through this process unchanged, especially as alternatives and drawbacks are shown. You can make edits, big and small, to the RFC to clarify or change the design, but make changes as new commits to the pull request, and leave a comment on the pull request explaining your changes. Specifically, do not squash or rebase commits after they are visible on the pull request.
-- At some point, a core maintainer will make a decision on the disposition for the RFC (merge, close, or postpone).
-  - This step is taken when enough of the tradeoffs have been discussed that the core maintainer is in a position to make a decision. That does not require consensus amongst all participants in the RFC thread (which is usually impossible). However, the argument supporting the disposition on the RFC needs to have already been clearly articulated, and there should not be a strong consensus against that position.
+- At some point, the subsystem maintainer will make a decision on the disposition for the RFC (merge, close, or postpone).
+  - This step is taken when enough of the tradeoffs have been discussed that the subsystem maintainer is in a position to make a decision. That does not require consensus amongst all participants in the RFC thread (which is usually impossible). However, the argument supporting the disposition on the RFC needs to have already been clearly articulated, and there should not be a strong consensus against that position.
 
 ## The RFC life-cycle
 [The RFC life-cycle]: #the-rfc-life-cycle
@@ -76,14 +85,14 @@ Furthermore, the fact that a given RFC has been accepted and is "active" implies
 
 Modifications to "active" RFCs can be done in follow-up pull requests. We strive to write each RFC in a manner that it will reflect the final design of the feature; but the nature of the process means that we cannot expect every merged RFC to actually reflect what the end result will be at the time of the next major release.
 
-In general, once accepted, RFCs should not be substantially changed. Only very minor changes should be submitted as amendments. More substantial changes should be new RFCs, with a note added to the original RFC. Exactly what counts as a "very minor change" is up to the core maintainers to decide.
+In general, once accepted, RFCs should not be substantially changed. Only very minor changes should be submitted as amendments. More substantial changes should be new RFCs, with a note added to the original RFC. Exactly what counts as a "very minor change" is up to the subsystem maintainers to decide.
 
 ## Reviewing RFCs
 [Reviewing RFCs]: #reviewing-rfcs
 
-While the RFC pull request is up, the core maintainers may schedule meetings with the author and/or relevant stakeholders to discuss the issues in greater detail, and the topic may be discussed at weekly meetings. In either case a summary from the meeting will be posted back to the RFC pull request.
+While the RFC pull request is up, the subsystem maintainers may schedule meetings with the author and/or relevant stakeholders to discuss the issues in greater detail, and the topic may be discussed at weekly meetings. In either case a summary from the meeting will be posted back to the RFC pull request.
 
-A core maintainer makes final decisions about RFCs after the benefits and drawbacks are well understood. These decisions can be made at any time, but the core maintainer will regularly issue decisions. When a decision is made, the RFC pull request will either be merged or closed. In either case, if the reasoning is not clear from the discussion in thread, the core maintainer will add a comment describing the rationale for the decision.
+The subsystem maintainer makes final decisions about RFCs after the benefits and drawbacks are well understood. These decisions can be made at any time, but the subsystem maintainer will regularly issue decisions. When a decision is made, the RFC pull request will either be merged or closed. In either case, if the reasoning is not clear from the discussion in thread, the subsystem maintainer will add a comment describing the rationale for the decision.
 
 ## Implementing an RFC
 [Implementing an RFC]: #implementing-an-rfc
@@ -97,7 +106,7 @@ If you are interested in working on the implementation for an "active" RFC, but
 ## RFC Postponement
 [RFC Postponement]: #rfc-postponement
 
-Some RFC pull requests are tagged with the "postponed" label when they are closed (as part of the rejection process). An RFC closed with "postponed" is marked as such because we want neither to think about evaluating the proposal nor about implementing the described feature until some time in the future, and we believe that we can afford to wait until then to do so. Postponed pull requests may be re-opened when the time is right. We don't have any formal process for that, you should ask a core maintainer.
+Some RFC pull requests are tagged with the "postponed" label when they are closed (as part of the rejection process). An RFC closed with "postponed" is marked as such because we want neither to think about evaluating the proposal nor about implementing the described feature until some time in the future, and we believe that we can afford to wait until then to do so. Postponed pull requests may be re-opened when the time is right. We don't have any formal process for that, you should ask the subsystem maintainer.
 
 Usually an RFC pull request marked as "postponed" has already passed an informal first round of evaluation, namely the round of "do we think we would ever possibly consider making this change, as outlined in the RFC pull request, or some semi-obvious variation of it." (When the answer to the latter question is "no", then the appropriate response is to close the RFC, not postpone it.)