MediaTek Gen2 PCIe controller which is available on MT7623 series SoCs

PCIe subsys supports single root complex (RC) with 3 Root Ports. Each root
ports supports a Gen2 1-lane Link and has PIPE interface to PHY.

Required properties:
- compatible: Should contain "mediatek,mt7623-pcie".
- device_type: Must be "pci"
- reg: Base addresses and lengths of the PCIe controller.
- #address-cells: Address representation for root ports (must be 3)
- #size-cells: Size representation for root ports (must be 2)
- #interrupt-cells: Size representation for interrupts (must be 1)
- interrupt-map-mask and interrupt-map: Standard PCI IRQ mapping properties
  Please refer to the standard PCI bus binding document for a more detailed
  explanation.
- clocks: Must contain an entry for each entry in clock-names.
  See ../clocks/clock-bindings.txt for details.
- clock-names: Must include the following entries:
  - free_ck :for reference clock of PCIe subsys
  - sys_ck0 :for clock of Port0
  - sys_ck1 :for clock of Port1
  - sys_ck2 :for clock of Port2
- resets: Must contain an entry for each entry in reset-names.
  See ../reset/reset.txt for details.
- reset-names: Must include the following entries:
  - pcie-rst0 :port0 reset
  - pcie-rst1 :port1 reset
  - pcie-rst2 :port2 reset
- phys: List of PHY specifiers (used by generic PHY framework).
- phy-names : Must be "pcie-phy0", "pcie-phy1", "pcie-phyN".. based on the
  number of PHYs as specified in *phys* property.
- power-domains: A phandle and power domain specifier pair to the power domain
  which is responsible for collapsing and restoring power to the peripheral.
- bus-range: Range of bus numbers associated with this controller.
- ranges: Ranges for the PCI memory and I/O regions.

In addition, the device tree node must have sub-nodes describing each
PCIe port interface, having the following mandatory properties:

Required properties:
- device_type: Must be "pci"
- reg: Only the first four bytes are used to refer to the correct bus number
  and device number.
- #address-cells: Must be 3
- #size-cells: Must be 2
- #interrupt-cells: Must be 1
- interrupt-map-mask and interrupt-map: Standard PCI IRQ mapping properties
  Please refer to the standard PCI bus binding document for a more detailed
  explanation.
- ranges: Sub-ranges distributed from the PCIe controller node. An empty
  property is sufficient.
- num-lanes: Number of lanes to use for this port.

Examples:

	hifsys: syscon@1a000000 {
		compatible = "mediatek,mt7623-hifsys",
			     "mediatek,mt2701-hifsys",
			     "syscon";
		reg = <0 0x1a000000 0 0x1000>;
		#clock-cells = <1>;
		#reset-cells = <1>;
	};

	pcie: pcie-controller@1a140000 {
		compatible = "mediatek,mt7623-pcie";
		device_type = "pci";
		reg = <0 0x1a140000 0 0x1000>, /* PCIe shared registers */
		      <0 0x1a142000 0 0x1000>, /* Port0 registers */
		      <0 0x1a143000 0 0x1000>, /* Port1 registers */
		      <0 0x1a144000 0 0x1000>; /* Port2 registers */
		#address-cells = <3>;
		#size-cells = <2>;
		#interrupt-cells = <1>;
		interrupt-map-mask = <0xf800 0 0 0>;
		interrupt-map = <0x0000 0 0 0 &sysirq GIC_SPI 193 IRQ_TYPE_LEVEL_LOW>,
				<0x0800 0 0 0 &sysirq GIC_SPI 194 IRQ_TYPE_LEVEL_LOW>,
				<0x1000 0 0 0 &sysirq GIC_SPI 195 IRQ_TYPE_LEVEL_LOW>;
		clocks = <&topckgen CLK_TOP_ETHIF_SEL>,
			 <&hifsys CLK_HIFSYS_PCIE0>,
			 <&hifsys CLK_HIFSYS_PCIE1>,
			 <&hifsys CLK_HIFSYS_PCIE2>;
		clock-names = "free_ck", "sys_ck0", "sys_ck1", "sys_ck2";
		resets = <&hifsys MT2701_HIFSYS_PCIE0_RST>,
			 <&hifsys MT2701_HIFSYS_PCIE1_RST>,
			 <&hifsys MT2701_HIFSYS_PCIE2_RST>;
		reset-names = "pcie-rst0", "pcie-rst1", "pcie-rst2";
		phys = <&pcie0_phy>, <&pcie1_phy>, <&pcie2_phy>;
		phy-names = "pcie-phy0", "pcie-phy1", "pcie-phy2";
		power-domains = <&scpsys MT2701_POWER_DOMAIN_HIF>;
		bus-range = <0x00 0xff>;
		ranges = <0x81000000 0 0x1a160000 0 0x1a160000 0 0x00010000	/* I/O space */
			  0x83000000 0 0x60000000 0 0x60000000 0 0x10000000>;	/* memory space */

		pcie@0,0 {
			device_type = "pci";
			reg = <0x0000 0 0 0 0>;
			#address-cells = <3>;
			#size-cells = <2>;
			#interrupt-cells = <1>;
			interrupt-map-mask = <0 0 0 0>;
			interrupt-map = <0 0 0 0 &sysirq GIC_SPI 193 IRQ_TYPE_LEVEL_LOW>;
			ranges;
			num-lanes = <1>;
		};

		pcie@1,0 {
			device_type = "pci";
			reg = <0x0800 0 0 0 0>;
			#address-cells = <3>;
			#size-cells = <2>;
			#interrupt-cells = <1>;
			interrupt-map-mask = <0 0 0 0>;
			interrupt-map = <0 0 0 0 &sysirq GIC_SPI 194 IRQ_TYPE_LEVEL_LOW>;
			ranges;
			num-lanes = <1>;
		};

		pcie@2,0 {
			device_type = "pci";
			reg = <0x1000 0 0 0 0>;
			#address-cells = <3>;
			#size-cells = <2>;
			#interrupt-cells = <1>;
			interrupt-map-mask = <0 0 0 0>;
			interrupt-map = <0 0 0 0 &sysirq GIC_SPI 195 IRQ_TYPE_LEVEL_LOW>;
			ranges;
			num-lanes = <1>;
		};
	};