add the ARM notification group (#740)

Author: nikomatsakis

src/SUMMARY.md

@@ -33,6 +33,7 @@
         - ["Cleanup Crew"](notification-groups/cleanup-crew.md)
         - [LLVM](notification-groups/llvm.md)
         - [Windows](notification-groups/windows.md)
+        - [ARM](notification-groups/arm.md)
     - [Licenses](./licenses.md)
 - [Part 2: High-level Compiler Architecture](./part-2-intro.md)
     - [Overview of the Compiler](./overview.md)

src/notification-groups/arm.md

@@ -0,0 +1,23 @@
+# ARM notification group
+
+**Github Label:** [O-ARM]
+
+[O-ARM]: https://github.com/rust-lang/rust/labels/O-ARM
+
+This list will be used to ask for help both in diagnosing and testing
+ARM-related issues as well as suggestions on how to resolve
+interesting questions regarding our ARM support.
+
+The group also has an associated Zulip stream (`#t-compiler/arm`)
+where people can go to pose questions and discuss ARM-specific
+topics.
+
+So, if you are interested in participating, please sign up for the
+ARM group! To do so, you open a PR against the [rust-lang/team]
+repository. Just [follow this example][eg], but change the username to
+your own!
+
+[rust-lang/team]: https://github.com/rust-lang/team
+[eg]: https://github.com/rust-lang/team/pull/358
+[#72569]: https://github.com/rust-lang/rust/pull/72569
+[#29520]: https://github.com/rust-lang/rust/pull/29520