[PATCH] GPIO core

This defines a simple and minimalist programming interface for GPIO APIs:

  - Documentation/gpio.txt ... describes things (read it)

  - include/asm-arm/gpio.h ... defines the ARM hook, which just punts
    to <asm/arch/gpio.h> for any implementation

  - include/asm-generic/gpio.h ... implement "can sleep" variants as calling
    the normal ones, for systems that don't handle i2c expanders.

The immediate need for such a cross-architecture API convention is to support
drivers that work the same on AT91 ARM and AVR32 AP7000 chips, which embed many
of the same controllers but have different CPUs.  However, several other users
have been reported, including a driver for a hardware watchdog chip and some
handhelds.org multi-CPU button drivers.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>