This adds a simple check that any compatible strings in DeviceTree dts
files are present in Documentation/devicetree/bindings and
in dts/Bindings/.

Vendor prefixes are also checked for existing in vendor-prefixes.txt.

This code is based on linux v4.0-rc6 checkpatch.pl dt-checking code by
Rob Herring & Florian Vaussard:

    Rob Herring (2):
        checkpatch: add DT compatible string documentation checks
        checkpatch: fix wildcard DT compatible string checking

    Florian Vaussard (3):
        checkpatch: fix spurious vendor compatible warnings
        checkpatch: check compatible strings in .c and .h too
        checkpatch: improve the compatible vendor match

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Florian Vaussard <florian.vaussard@epfl.ch>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>