Documentation/devicetree/bindings/gpio/gpio.txt

Specifying GPIO information for devices
============================================

1) gpios property
-----------------

Nodes that makes use of GPIOs should define them using `gpios' property,
format of which is: <&gpio-controller1-phandle gpio1-specifier
		     &gpio-controller2-phandle gpio2-specifier
		     0 /* holes are permitted, means no GPIO 3 */
		     &gpio-controller4-phandle gpio4-specifier
		     ...>;

Note that gpio-specifier length is controller dependent.

gpio-specifier may encode: bank, pin position inside the bank,
whether pin is open-drain and whether pin is logically inverted.

Example of the node using GPIOs:

	node {
		gpios = <&qe_pio_e 18 0>;
	};

In this example gpio-specifier is "18 0" and encodes GPIO pin number,
and empty GPIO flags as accepted by the "qe_pio_e" gpio-controller.

2) gpio-controller nodes
------------------------

Every GPIO controller node must have #gpio-cells property defined,
this information will be used to translate gpio-specifiers.

Example of two SOC GPIO banks defined as gpio-controller nodes:

	qe_pio_a: gpio-controller@1400 {
		#gpio-cells = <2>;
		compatible = "fsl,qe-pario-bank-a", "fsl,qe-pario-bank";
		reg = <0x1400 0x18>;
		gpio-controller;
	};

	qe_pio_e: gpio-controller@1460 {
		#gpio-cells = <2>;
		compatible = "fsl,qe-pario-bank-e", "fsl,qe-pario-bank";
		reg = <0x1460 0x18>;
		gpio-controller;
	};