Again only minimal changes to make kerneldoc no longer shout. Plus a
little introduction in the form of a inline DOC: section to quickly
explain what this is all about.

v2: Fixup spelling fail.
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NDave Airlie <airlied@redhat.com>