linux/Documentation/devicetree/bindings/gpio/pl061-gpio.txt
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   1ARM PL061 GPIO controller
   2
   3Required properties:
   4- compatible : "arm,pl061", "arm,primecell"
   5- #gpio-cells : Should be two. The first cell is the pin number and the
   6  second cell is used to specify optional parameters:
   7  - bit 0 specifies polarity (0 for normal, 1 for inverted)
   8- gpio-controller : Marks the device node as a GPIO controller.
   9- interrupts : Interrupt mapping for GPIO IRQ.
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