doc: update drm-tip repository documentation

Brush up, remove duplication, add links.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>

repositories/drm-tip.rst

@@ -4,21 +4,7 @@
 drm-tip
 =======
 
-The drm-tip branch (in the drm-tip repository) is the common DRM subsystem
-testing and integration tree (or "pile" to complete the reverse acronym). It's a
-bit like linux-next for graphics. It gets rebuilt every time one of the branches
-maintained using dim is updated.
-
-It should be emphasized that no patch ever gets pushed to drm-tip directly,
-drm-tip is not upstream per se, and no pull requests are ever sent to or from
-drm-tip. It is, however, the merge result of a number of upstream branches like
-that. It is the combined bleeding edge of kernel graphics.
-
-The drm-rerere branch contains the `nightly.conf`_ configuration file that
-describes the branches that get merged to drm-tip, as well as shared conflict
-resolution for merging the branches on drm-tip rebuild.
-
-.. _nightly.conf: https://gitlab.freedesktop.org/drm/tip/-/blob/rerere-cache/nightly.conf
+The DRM subsystem configuration and integration repository.
 
 Repository and Branches
 =======================
@@ -28,17 +14,27 @@ https://gitlab.freedesktop.org/drm/tip
 drm-tip
 -------
 
-This is the overall integration tree for drm, and lives in
-``https://gitlab.freedesktop.org/drm/tip.git``. Every time one of the above
-branches is updated drm-tip gets rebuilt. If there's a conflict see section on
-`resolving conflicts when rebuilding drm-tip
-<drm-tip.html#resolving-conflicts-when-rebuilding-drm-tip>`_.
+The drm-tip branch is the common DRM subsystem testing and integration tree (or
+"pile" to complete the reverse acronym). It's a bit like linux-next for
+graphics. It gets automatically rebuilt and pushed every time one of the
+branches maintained using :doc:`/dim` is updated.
+
+It should be emphasized that no patch ever gets pushed to drm-tip directly,
+drm-tip is not upstream per se, and no pull requests are ever sent to or from
+drm-tip. It is, however, the merge result of a number of upstream branches like
+that. It is the combined bleeding edge of kernel graphics.
+
+It is generally recommended to do graphics subsystem development on top of
+drm-tip.
 
 drm-rerere
 ----------
 
-This branch contains the `nightly.conf`_ configuration file and the shared ``git
-rerere`` conflict resolutions for dim to generate drm-tip, as well as some
-kernel defconfig files for build testing.
+The drm-rerere branch contains the `nightly.conf`_ configuration file that
+describes the repositories and branches managed by :doc:`/dim` that get merged
+to drm-tip, the shared `git rerere`_ conflict resolutions for :doc:`/dim` to
+generate drm-tip, as well as some kernel defconfig files for build testing.
 
 .. _nightly.conf: https://gitlab.freedesktop.org/drm/tip/-/blob/rerere-cache/nightly.conf
+
+.. _git rerere: https://git-scm.com/docs/git-rerere