Renesas HSPI.

Required properties:
- compatible       : "renesas,hspi-<soctype>", "renesas,hspi" as fallback.
		     Examples with soctypes are:
		       - "renesas,hspi-r8a7778" (R-Car M1)
		       - "renesas,hspi-r8a7779" (R-Car H1)
- reg              : Offset and length of the register set for the device
- interrupts       : Interrupt specifier
- #address-cells   : Must be <1>
- #size-cells      : Must be <0>

Pinctrl properties might be needed, too.  See
Documentation/devicetree/bindings/pinctrl/renesas,*.

Example:

	hspi0: spi@fffc7000 {
		compatible = "renesas,hspi-r8a7778", "renesas,hspi";
		reg = <0xfffc7000 0x18>;
		interrupt-parent = <&gic>;
		interrupts = <0 63 IRQ_TYPE_LEVEL_HIGH>;
		#address-cells = <1>;
		#size-cells = <0>;
	};

