media: doc-rst: add more info for resolution change blocks in ipu3

This patch add more details for the resolution change blocks
It can help the developer to understand the main resolution
change blocks in ImgU.

[sakari.ailus@linux.intel.com: Add new files to MAINTAINERS]

Signed-off-by: Bingbu Cao <bingbu.cao@intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>