pinctrl: Add DT bindings for PIC32 pin control and GPIO

* Microchip PIC32 GPIO devices (PIO).

Required properties:

 - compatible: "microchip,pic32mzda-gpio"

 - reg: Base address and length for the device.

 - interrupts: The port interrupt shared by all pins.

 - gpio-controller: Marks the port as GPIO controller.

 - #gpio-cells: Two. The first cell is the pin number and

   the second cell is used to specify the gpio polarity as defined in

   defined in <dt-bindings/gpio/gpio.h>:

      0 = GPIO_ACTIVE_HIGH

      1 = GPIO_ACTIVE_LOW

      2 = GPIO_OPEN_DRAIN

 - interrupt-controller: Marks the device node as an interrupt controller.

 - #interrupt-cells: Two. The first cell is the GPIO number and second cell

   is used to specify the trigger type as defined in

   <dt-bindings/interrupt-controller/irq.h>:

      IRQ_TYPE_EDGE_RISING

      IRQ_TYPE_EDGE_FALLING

      IRQ_TYPE_EDGE_BOTH

 - clocks: Clock specifier (see clock bindings for details).

 - microchip,gpio-bank: Specifies which bank a controller owns.

 - gpio-ranges: Interaction with the PINCTRL subsystem.

Example:

/* PORTA */

gpio0: gpio0@1f860000 {

	compatible = "microchip,pic32mzda-gpio";

	reg = <0x1f860000 0x100>;

	interrupts = <118 IRQ_TYPE_LEVEL_HIGH>;

	#gpio-cells = <2>;

	gpio-controller;

	interrupt-controller;

	#interrupt-cells = <2>;

	clocks = <&PBCLK4>;

	microchip,gpio-bank = <0>;

	gpio-ranges = <&pic32_pinctrl 0 0 16>;

};

keys {

	...

	button@sw1 {

		label = "ESC";

		linux,code = <1>;

		gpios = <&gpio0 12 0>;

	};

};

* Microchip PIC32 Pin Controller

Please refer to pinctrl-bindings.txt, ../gpio/gpio.txt, and

../interrupt-controller/interrupts.txt for generic information regarding

pin controller, GPIO, and interrupt bindings.

PIC32 'pin configuration node' is a node of a group of pins which can be

used for a specific device or function. This node represents configuraions of

pins, optional function, and optional mux related configuration.

Required properties for pin controller node:

 - compatible: "microchip,pic32mada-pinctrl"

 - reg: Address range of the pinctrl registers.

 - clocks: Clock specifier (see clock bindings for details)

Required properties for pin configuration sub-nodes:

 - pins: List of pins to which the configuration applies.

Optional properties for pin configuration sub-nodes:

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

 - function: Mux function for the specified pins.

 - bias-pull-up: Enable weak pull-up.

 - bias-pull-down: Enable weak pull-down.

 - input-enable: Set the pin as an input.

 - output-low: Set the pin as an output level low.

 - output-high: Set the pin as an output level high.

 - microchip,digital: Enable digital I/O.

 - microchip,analog: Enable analog I/O.

Example:

pic32_pinctrl: pinctrl@1f801400{

	#address-cells = <1>;

	#size-cells = <1>;

	compatible = "microchip,pic32mzda-pinctrl";

	reg = <0x1f801400 0x400>;

	clocks = <&PBCLK1>;

	pinctrl_uart2: pinctrl_uart2 {

		uart2-tx {

			pins = "G9";

			function = "U2TX";

			microchip,digital;

			output-low;

		};

		uart2-rx {

			pins = "B0";

			function = "U2RX";

			microchip,digital;

			input-enable;

		};

	};

};

uart2: serial@1f822200 {

	compatible = "microchip,pic32mzda-uart";

	reg = <0x1f822200 0x50>;

	pinctrl-names = "default";

	pinctrl-0 = <&pinctrl_uart2>;

};