pinctrl: add DT binding doc for pincontrol of PMIC max77620/max20024

Pincontrol driver for MAX77620 Power management IC from Maxim Semiconductor.

Device has 8 GPIO pins which can be configured as GPIO as well as the

special IO functions.

Please refer file <devicetree/bindings/pinctrl/pinctrl-bindings.txt>

for details of the common pinctrl bindings used by client devices,

including the meaning of the phrase "pin configuration node".

Optional Pinmux properties:

--------------------------

Following properties are required if default setting of pins are required

at boot.

- pinctrl-names: A pinctrl state named per <pinctrl-binding.txt>.

- pinctrl[0...n]: Properties to contain the phandle for pinctrl states per

		<pinctrl-binding.txt>.

The pin configurations are defined as child of the pinctrl states node. Each

sub-node have following properties:

Required properties:

------------------

- pins: List of pins. Valid values of pins properties are:

		      gpio0, gpio1, gpio2, gpio3, gpio4, gpio5, gpio6, gpio7.

Optional properties:

-------------------

Following are optional properties defined as pinmux DT binding document

<pinctrl-bindings.txt>. Absence of properties will leave the configuration

on default.

	function,

	drive-push-pull,

	drive-open-drain,

	bias-pull-up,

	bias-pull-down.

Valid values for function properties are:

	gpio, lpm-control-in, fps-out, 32k-out, sd0-dvs-in, sd1-dvs-in,

	reference-out

Theres is also customised properties for the GPIO1, GPIO2 and GPIO3. These

customised properties are required to configure FPS configuration parameters

of these GPIOs. Please refer <devicetree/bindings/mfd/max77620.txt> for more

detail of Flexible Power Sequence (FPS).

- maxim,active-fps-source:		FPS source for the GPIOs to get

					enabled/disabled when system is in

					active state.  Valid values are:

					- MAX77620_FPS_SRC_0,

						FPS source is FPS0.

					- MAX77620_FPS_SRC_1,

						FPS source is FPS1

					- MAX77620_FPS_SRC_2 and

						FPS source is FPS2

					- MAX77620_FPS_SRC_NONE.

						GPIO is not controlled

						by FPS events and it gets

						enabled/disabled by register

						access.

					Absence of this property will leave

					the FPS configuration register for that

					GPIO to default configuration.

- maxim,active-fps-power-up-slot:	Sequencing event slot number on which

					the GPIO get enabled when

					master FPS input event set to HIGH.

					Valid values are 0 to 7.

					This is applicable if FPS source is

					selected as FPS0, FPS1 or FPS2.

- maxim,active-fps-power-down-slot:	Sequencing event slot number on which

					the GPIO get disabled when master

					FPS input event set to LOW.

					Valid values are 0 to 7.

					This is applicable if FPS source is

					selected as FPS0, FPS1 or FPS2.

- maxim,suspend-fps-source:		This is same as property

					"maxim,active-fps-source" but value

					get configured when system enters in

					to suspend state.

- maxim,suspend-fps-power-up-slot:	This is same as property

					"maxim,active-fps-power-up-slot" but

					this value get configured into FPS

					configuration register when system

					enters into suspend.

					This is applicable if suspend state

					FPS source is selected as FPS0, FPS1 or

- maxim,suspend-fps-power-down-slot:	This is same as property

					"maxim,active-fps-power-down-slot" but

					this value get configured into FPS

					configuration register when system

					enters into suspend.

					This is applicable if suspend state

					FPS source is selected as FPS0, FPS1 or

					FPS2.

Example:

--------

#include <dt-bindings/mfd/max77620.h>

...

max77620@3c {

	pinctrl-names = "default";

	pinctrl-0 = <&spmic_default>;

	spmic_default: pinmux@0 {

		pin_gpio0 {

			pins = "gpio0";

			function = "gpio";

		};

		pin_gpio1 {

			pins = "gpio1";

			function = "fps-out";

			maxim,active-fps-source = <MAX77620_FPS_SRC_0>;

		};

		pin_gpio2 {

			pins = "gpio2";

			function = "fps-out";

			maxim,active-fps-source = <MAX77620_FPS_SRC_1>;

		};

	};

};