linux/Documentation/devicetree/bindings/gpio/gpio-74x164.txt
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   1* Generic 8-bits shift register GPIO driver
   2
   3Required properties:
   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:
   9      0 = active high
  10      1 = active low
  11- registers-number: Number of daisy-chained shift registers
  12
  13Example:
  14
  15gpio5: gpio5@0 {
  16        compatible = "fairchild,74hc595";
  17        reg = <0>;
  18        gpio-controller;
  19        #gpio-cells = <2>;
  20        registers-number = <4>;
  21        spi-max-frequency = <100000>;
  22};
  23