dt-bindings: Add GPCv2 power gating driver

Freescale i.MX General Power Controller v2

==========================================

The i.MX7S/D General Power Control (GPC) block contains Power Gating

Control (PGC) for various power domains.

Required properties:

- compatible: Should be "fsl,imx7d-gpc"

- reg: should be register base and length as documented in the

  datasheet

- interrupts: Should contain GPC interrupt request 1

Power domains contained within GPC node are generic power domain

providers, documented in

Documentation/devicetree/bindings/power/power_domain.txt, which are

described as subnodes of the power gating controller 'pgc' node,

which, in turn, is expected to contain the following:

Required properties:

- reg: Power domain index. Valid values are defined in

  include/dt-bindings/power/imx7-power.h

- #power-domain-cells: Should be 0

Optional properties:

- power-supply: Power supply used to power the domain

Example:

	gpc: gpc@303a0000 {

		compatible = "fsl,imx7d-gpc";

		reg = <0x303a0000 0x1000>;

		interrupt-controller;

		interrupts = <GIC_SPI 87 IRQ_TYPE_LEVEL_HIGH>;

		#interrupt-cells = <3>;

		interrupt-parent = <&intc>;

		pgc {

			#address-cells = <1>;

			#size-cells = <0>;

			pgc_pcie_phy: power-domain@3 {

				#power-domain-cells = <0>;

				reg = <IMX7_POWER_DOMAIN_PCIE_PHY>;

				power-supply = <&reg_1p0d>;

			};

		};

	};

Specifying power domain for IP modules

======================================

IP cores belonging to a power domain should contain a 'power-domains'

property that is a phandle for PGC node representing the domain.

Example of a device that is part of the PCIE_PHY power domain:

	pcie: pcie@33800000 {

	      reg = <0x33800000 0x4000>,

	            <0x4ff00000 0x80000>;

		/* ... */

		power-domains = <&pgc_pcie_phy>;

		/* ... */

	};

/*

 *  Copyright (C) 2017 Impinj

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 */

#ifndef __DT_BINDINGS_IMX7_POWER_H__

#define __DT_BINDINGS_IMX7_POWER_H__

#define IMX7_POWER_DOMAIN_MIPI_PHY		0

#define IMX7_POWER_DOMAIN_PCIE_PHY		1

#define IMX7_POWER_DOMAIN_USB_HSIC_PHY		2

#endif