gpu: nova-core: add initial documentation

Add the initial documentation of the Nova project.

The initial project documentation consists out of a brief introduction
of the project, as well as project guidelines both general and nova-core
specific and a task list for nova-core specifically.

The task list is divided into tasks for general Rust infrastructure
required by the project, tasks regarding GSP enablement and firmware
abstraction, general GPU driver tasks as well as tasks related to
external API design and test infrastructure.

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://lore.kernel.org/r/20250306222336.23482-6-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Author: Danilo Krummrich

Documentation/gpu/drivers.rst

@@ -24,6 +24,7 @@ GPU Driver Documentation
    panfrost
    panthor
    zynqmp
+   nova/index
 
 .. only::  subproject and html
 

Documentation/gpu/nova/core/guidelines.rst

@@ -0,0 +1,24 @@
+.. SPDX-License-Identifier: (GPL-2.0+ OR MIT)
+
+==========
+Guidelines
+==========
+
+This documents contains the guidelines for nova-core. Additionally, all common
+guidelines of the Nova project do apply.
+
+Driver API
+==========
+
+One main purpose of nova-core is to implement the abstraction around the
+firmware interface of GSP and provide a firmware (version) independent API for
+2nd level drivers, such as nova-drm or the vGPU manager VFIO driver.
+
+Therefore, it is not permitted to leak firmware (version) specifics, through the
+driver API, to 2nd level drivers.
+
+Acceptance Criteria
+===================
+
+- To the extend possible, patches submitted to nova-core must be tested for
+  regressions with all 2nd level drivers.