Add io-mapping.rst under Documentation/driver-api and reference it from
Sphinx TOC Tree present in Documentation/driver-api/index.rst
Signed-off-by: NPragat Pandya <pragat.pandya@gmail.com>
Link: https://lore.kernel.org/r/20200303050301.5412-2-pragat.pandya@gmail.comSigned-off-by: NJonathan Corbet <corbet@lwn.net>