This patchset introduces a new custom directive called 'drivers-doc'
which loads all available drivers under a given namespace and import
their respective docstring into the .rst document.
This patchset also contains some modification/addition to the
docstring of these drivers to make the final document complete.
Change-Id: Ib3df59fa45cea9d11d20fb73a5f0f1d564135bca
Closes-Bug: #1536218
Closes-Bug: #1536735
98a65efb16