Docs: sphinxify device-drivers.tmpl

Perform a basic sphinx conversion of the device-drivers docbook and move it
to its own directory.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/DocBook/Makefile

@@ -6,7 +6,7 @@
 # To add a new book the only step required is to add the book to the
 # list of DOCBOOKS.
 
-DOCBOOKS := z8530book.xml device-drivers.xml \
+DOCBOOKS := z8530book.xml  \
 	    kernel-hacking.xml kernel-locking.xml deviceiobook.xml \
 	    writing_usb_driver.xml networking.xml \
 	    kernel-api.xml filesystems.xml lsm.xml usb.xml kgdb.xml \

Documentation/index.rst

@@ -13,6 +13,7 @@ Contents:
 
    kernel-documentation
    dev-tools/tools
+   driver-api/drivers
    media/index
    gpu/index