This includes SPI compatible devices like SN74165 serial-out shift
registers and the SN65HVS88x series of industrial serializers that can
be read over the SPI bus and used for GPI (General Purpose Input).
Signed-off-by: Andrew F. Davis <afd@ti.com> Tested-by: Sean Nyekjaer <sean.nyekjaer@prevas.dk> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>