spi/davinci: add DT binding documentation

Add binding documentation for spi-davinci module.

[prakash.pm@ti.com: Follow DT naming convention for compatible property]
Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Manjunathappa, Prakash <prakash.pm@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>

Documentation/devicetree/bindings/spi/spi-davinci.txt

@@ -0,0 +1,51 @@
+Davinci SPI controller device bindings
+
+Required properties:
+- #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.
+- compatible:
+	- "ti,dm6441-spi" for SPI used similar to that on DM644x SoC family
+	- "ti,da830-spi" for SPI used similar to that on DA8xx SoC family
+- reg: Offset and length of SPI controller register space
+- num-cs: Number of chip selects
+- ti,davinci-spi-intr-line: interrupt line used to connect the SPI
+	IP to the interrupt controller within the SoC. Possible values
+	are 0 and 1. Manual says one of the two possible interrupt
+	lines can be tied to the interrupt controller. Set this
+	based on a specifc SoC configuration.
+- interrupts: interrupt number mapped to CPU.
+- clocks: spi clk phandle
+
+Example of a NOR flash slave device (n25q032) connected to DaVinci
+SPI controller device over the SPI bus.
+
+spi0:spi@20BF0000 {
+	#address-cells			= <1>;
+	#size-cells			= <0>;
+	compatible			= "ti,dm6446-spi";
+	reg				= <0x20BF0000 0x1000>;
+	num-cs				= <4>;
+	ti,davinci-spi-intr-line	= <0>;
+	interrupts			= <338>;
+	clocks				= <&clkspi>;
+
+	flash: n25q032@0 {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		compatible = "st,m25p32";
+		spi-max-frequency = <25000000>;
+		reg = <0>;
+
+		partition@0 {
+			label = "u-boot-spl";
+			reg = <0x0 0x80000>;
+			read-only;
+		};
+
+		partition@1 {
+			label = "test";
+			reg = <0x80000 0x380000>;
+		};
+	};
+};