spi: bcm2835aux: spi: add bindings for the bcm2835 auxiliary spi devices

This defines the spi1 and spi2 devices in the device-tree.
Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/spi/brcm,bcm2835-aux-spi.txt

+Broadcom BCM2835 auxiliar SPI1/2 controller
+
+The BCM2835 contains two forms of SPI master controller, one known simply as
+SPI0, and the other known as the "Universal SPI Master"; part of the
+auxiliary block. This binding applies to the SPI1/2 controller.
+
+Required properties:
+- compatible: Should be "brcm,bcm2835-aux-spi".
+- reg: Should contain register location and length for the spi block
+- interrupts: Should contain shared interrupt of the aux block
+- clocks: The clock feeding the SPI controller - needs to
+	  point to the auxiliar clock driver of the bcm2835,
+	  as this clock will enable the output gate for the specific
+	  clock.
+- cs-gpios: the cs-gpios (native cs is NOT supported)
+	    see also spi-bus.txt
+
+Example:
+
+spi1@7e215080 {
+	compatible = "brcm,bcm2835-aux-spi";
+	reg = <0x7e215080 0x40>;
+	interrupts = <1 29>;
+	clocks = <&aux_clocks BCM2835_AUX_CLOCK_SPI1>;
+	#address-cells = <1>;
+	#size-cells = <0>;
+	cs-gpios = <&gpio 18>, <&gpio 17>, <&gpio 16>;
+};
+
+spi2@7e2150c0 {
+	compatible = "brcm,bcm2835-aux-spi";
+	reg = <0x7e2150c0 0x40>;
+	interrupts = <1 29>;
+	clocks = <&aux_clocks BCM2835_AUX_CLOCK_SPI2>;
+	#address-cells = <1>;
+	#size-cells = <0>;
+	cs-gpios = <&gpio 43>, <&gpio 44>, <&gpio 45>;
+};