Qualcomm Universal Peripheral (QUP) Serial Peripheral Interface (SPI)

The QUP core is an AHB slave that provides a common data path (an output FIFO
and an input FIFO) for serial peripheral interface (SPI) mini-core.

SPI in master mode supports up to 50MHz, up to four chip selects, programmable
data path from 4 bits to 32 bits and numerous protocol variants.

Required properties:
- compatible:     Should contain "qcom,spi-qup-v2.1.1" or "qcom,spi-qup-v2.2.1"
- reg:            Should contain base register location and length
- interrupts:     Interrupt number used by this controller

- clocks:         Should contain the core clock and the AHB clock.
- clock-names:    Should be "core" for the core clock and "iface" for the
                  AHB clock.

- #address-cells: Number of cells required to define a chip select
                  address on the SPI bus. Should be set to 1.
- #size-cells:    Should be zero.

Optional properties:
- spi-max-frequency: Specifies maximum SPI clock frequency,
                     Units - Hz. Definition as per
                     Documentation/devicetree/bindings/spi/spi-bus.txt

SPI slave nodes must be children of the SPI master node and can contain
properties described in Documentation/devicetree/bindings/spi/spi-bus.txt

Example:

	spi_8: spi@f9964000 { /* BLSP2 QUP2 */

		compatible = "qcom,spi-qup-v2";
		#address-cells = <1>;
		#size-cells = <0>;
		reg = <0xf9964000 0x1000>;
		interrupts = <0 102 0>;
		spi-max-frequency = <19200000>;

		clocks = <&gcc GCC_BLSP2_QUP2_SPI_APPS_CLK>, <&gcc GCC_BLSP2_AHB_CLK>;
		clock-names = "core", "iface";

		pinctrl-names = "default";
		pinctrl-0 = <&spi8_default>;

		device@0 {
			compatible = "arm,pl022-dummy";
			#address-cells = <1>;
			#size-cells = <1>;
			reg = <0>; /* Chip select 0 */
			spi-max-frequency = <19200000>;
			spi-cpol;
		};

		device@1 {
			compatible = "arm,pl022-dummy";
			#address-cells = <1>;
			#size-cells = <1>;
			reg = <1>; /* Chip select 1 */
			spi-max-frequency = <9600000>;
			spi-cpha;
		};

		device@2 {
			compatible = "arm,pl022-dummy";
			#address-cells = <1>;
			#size-cells = <1>;
			reg = <2>; /* Chip select 2 */
			spi-max-frequency = <19200000>;
			spi-cpol;
			spi-cpha;
		};

		device@3 {
			compatible = "arm,pl022-dummy";
			#address-cells = <1>;
			#size-cells = <1>;
			reg = <3>; /* Chip select 3 */
			spi-max-frequency = <19200000>;
			spi-cpol;
			spi-cpha;
			spi-cs-high;
		};
	};