dt-bindings: PCI: hisi: Add document for PCIe of Kirin SoCs

HiSilicon Kirin SoCs PCIe host DT description

Kirin PCIe host controller is based on Designware PCI core.

It shares common functions with PCIe Designware core driver

and inherits common properties defined in

Documentation/devicetree/bindings/pci/designware-pci.txt.

Additional properties are described here:

Required properties

- compatible:

	"hisilicon,kirin960-pcie" for PCIe of Kirin960 SoC

- reg: Should contain rc_dbi, apb, phy, config registers location and length.

- reg-names: Must include the following entries:

  "dbi": controller configuration registers;

  "apb": apb Ctrl register defined by Kirin;

  "phy": apb PHY register defined by Kirin;

  "config": PCIe configuration space registers.

- reset-gpios: The gpio to generate PCIe perst assert and deassert signal.

Optional properties:

Example based on kirin960:

	pcie@f4000000 {

		compatible = "hisilicon,kirin-pcie";

		reg = <0x0 0xf4000000 0x0 0x1000>, <0x0 0xff3fe000 0x0 0x1000>,

		      <0x0 0xf3f20000 0x0 0x40000>, <0x0 0xF4000000 0 0x2000>;

		reg-names = "dbi","apb","phy", "config";

		bus-range = <0x0  0x1>;

		#address-cells = <3>;

		#size-cells = <2>;

		device_type = "pci";

		ranges = <0x02000000 0x0 0x00000000 0x0 0xf5000000 0x0 0x2000000>;

		num-lanes = <1>;

		#interrupt-cells = <1>;

		interrupt-map-mask = <0xf800 0 0 7>;

		interrupt-map = <0x0 0 0 1 &gic 0 0 0  282 4>,

				<0x0 0 0 2 &gic 0 0 0  283 4>,

				<0x0 0 0 3 &gic 0 0 0  284 4>,

				<0x0 0 0 4 &gic 0 0 0  285 4>;

		clocks = <&crg_ctrl HI3660_PCIEPHY_REF>,

			 <&crg_ctrl HI3660_CLK_GATE_PCIEAUX>,

			 <&crg_ctrl HI3660_PCLK_GATE_PCIE_PHY>,

			 <&crg_ctrl HI3660_PCLK_GATE_PCIE_SYS>,

			 <&crg_ctrl HI3660_ACLK_GATE_PCIE>;

		clock-names = "pcie_phy_ref", "pcie_aux",

			      "pcie_apb_phy", "pcie_apb_sys", "pcie_aclk";

		reset-gpios = <&gpio11 1 0 >;

	};