drm/doc/rfc: Introduce the merge plan for the Xe driver.

drm/doc/rfc: Introduce the merge plan for the Xe driver.

Let’s establish a merge plan for Xe, by writing down clear pre-merge goals, in
order to avoid unnecessary delays.

This initial document starts with a TODO list containing items with clear and
measurable key results. Xe’s initial pull request should only be sent to
dri-devel after all the items are clearly resolved.

Since many of them involve some level of a community consensus, in many cases,
the consensus will be reached in follow-up patches to this document with more
details of the API or helpers that will be developed or modified.

Besides of the items that are highlighted in this document, it is important
to highlight that Oded, has been volunteered to give the overall ack on Xe
driver as the way to confirm that it looks good for upstream.

v2: Incorporated Daniel's feedback:
    - Do not make long-running compute a blocker.
    - Add a mention to drm-exec that that ties to vm_bind and long-running
      compute jobs. Then I also added GPUVA since I recently noticed that this
      ties also to the work Matt is doing on that front.
    - Added the devcoredump section.
    - Add the mention to Oded being volunteered for the overall ack.

v3: Reword a bit the Async VM_BIND to incorporate Daniel's feedback on ensuring
    the async vmbind consensus explicitly include Mesa, besides other kernel
    drivers.

Cc: Dave Airlie <airlied@redhat.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Francois Dugast <francois.dugast@intel.com>
Signed-off-by: Luis Strano <luis.strano@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230419191913.158807-1-rodrigo.vivi@intel.com