docs: add a minimal docs page for radv

RADV is the last driver in Mesa that doesn't have a webpage somewhere
that we can link to from mesa3d.org. So let's make a minimal docs article
for it where we link to relevant information elsewhere.

Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15494>

docs/drivers/radv.rst

@@ -0,0 +1,23 @@
+RADV
+====
+
+RADV is a Vulkan driver for AMD GCN/RDNA GPUs.
+
+Debugging
+---------
+
+For a list of environment variables to debug RADV, please see
+:ref:`radv env-vars` for a list.
+
+Hardware Documentation
+----------------------
+
+You can find a list of documentation for the various generations of
+AMD hardware on the `X.Org wiki
+<https://www.x.org/wiki/RadeonFeature/#documentation>`_.
+
+ACO
+---
+
+ACO is the shader-compiler used in RADV. You read its documentation
+`here <https://gitlab.freedesktop.org/mesa/mesa/-/blob/main/src/amd/compiler/README.md>`_.

docs/envvars.rst

@@ -600,6 +600,9 @@ VC4 driver environment variables
    ``dump``
       write a GPU command stream trace file (VC4 simulator only)
 
+
+.. _radv env-vars:
+
 RADV driver environment variables
 ---------------------------------
 

docs/index.rst

@@ -89,6 +89,7 @@ Linux, FreeBSD, and other operating systems.
    drivers/lima
    drivers/llvmpipe
    drivers/panfrost
+   drivers/radv
    drivers/svga3d
    drivers/v3d
    drivers/vc4