This converts the plain text documentation to reStructuredText format
and adds it to Sphinx TOC tree.

No essential content change.
Signed-off-by: NChangbin Du <changbin.du@gmail.com>
Reviewed-by: NMauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>