Merge branch 'driver-api' into doc/4.9

This short series convers device-drivers.tmpl into the RST format, splits
it up, and sets up the result under Documentation/driver-api/.  For added
fun, I've taken one top-level file (hsi.txt) and folded it into the
document as a way of showing the direction I'm thinking I would like things
to go.  There is plenty more of this sort of work that could be done, to
say the least - this is just a beginning!

The formatted results can be seen at:

    http://static.lwn.net/kerneldoc/driver-api/index.html

As part of the long-term task to turn Documentation/ into less of a horror
movie, I'd like to collect documentation of the driver-specific API here.
Arguably gpu/ and the media API stuff should eventually move here, though
we can discuss the color of that particular shed some other day.
Meanwhile, I'd appreciate comments on the general idea.

diff --cc Documentation/DocBook/Makefile
Simple merge