1 * Generic 8-bits shift register GPIO driver
4 - compatible : Should be "fairchild,74hc595"
5 - reg : chip select number
6 - gpio-controller : Marks the device node as a gpio controller.
7 - #gpio-cells : Should be two. The first cell is the pin number and
8 the second cell is used to specify the gpio polarity:
11 - registers-number: Number of daisy-chained shift registers
16 compatible = "fairchild,74hc595";
20 registers-number = <4>;
21 spi-max-frequency = <100000>;