linux-wandboard

MFD/OF: document MFD devices and handle simple-mfd

commit 22869a9eca4ea5b534538d160b68c7aef44e378a upstream.

This defines a new compatible option for MFD devices "simple-mfd" that will
make the OF core spawn child devices for all subnodes of that MFD device.
It is optional but handy for things like syscon and possibly other
simpler MFD devices.

Since there was no file to put the documentation in, I took this opportunity
to make a small writeup on MFD devices and add the compatible definition
there.

Suggested-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Devicetree <devicetree@vger.kernel.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
Cc: Kumar Gala <galak@codeaurora.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Henrik Juul Pedersen <hjp@liab.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>