spi: s3c64xx: add device tree support

Add support for device based discovery.
Signed-off-by: Thomas Abraham <thomas.abraham@linaro.org>
Acked-by: Jaswinder Singh <jaswinder.singh@linaro.org>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

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

+* Samsung SPI Controller
+
+The Samsung SPI controller is used to interface with various devices such as flash
+and display controllers using the SPI communication interface.
+
+Required SoC Specific Properties:
+
+- compatible: should be one of the following.
+    - samsung,s3c2443-spi: for s3c2443, s3c2416 and s3c2450 platforms
+    - samsung,s3c6410-spi: for s3c6410 platforms
+    - samsung,s5p6440-spi: for s5p6440 and s5p6450 platforms
+    - samsung,s5pv210-spi: for s5pv210 and s5pc110 platforms
+    - samsung,exynos4210-spi: for exynos4 and exynos5 platforms
+
+- reg: physical base address of the controller and length of memory mapped
+  region.
+
+- interrupts: The interrupt number to the cpu. The interrupt specifier format
+  depends on the interrupt controller.
+
+- tx-dma-channel: The dma channel specifier for tx operations. The format of
+  the dma specifier depends on the dma controller.
+
+- rx-dma-channel: The dma channel specifier for rx operations. The format of
+  the dma specifier depends on the dma controller.
+
+Required Board Specific Properties:
+
+- #address-cells: should be 1.
+- #size-cells: should be 0.
+- gpios: The gpio specifier for clock, mosi and miso interface lines (in the
+  order specified). The format of the gpio specifier depends on the gpio
+  controller.
+
+Optional Board Specific Properties:
+
+- samsung,spi-src-clk: If the spi controller includes a internal clock mux to
+  select the clock source for the spi bus clock, this property can be used to
+  indicate the clock to be used for driving the spi bus clock. If not specified,
+  the clock number 0 is used as default.
+
+- num-cs: Specifies the number of chip select lines supported. If
+  not specified, the default number of chip select lines is set to 1.
+
+SPI Controller specific data in SPI slave nodes:
+
+- The spi slave nodes should provide the following information which is required
+  by the spi controller.
+
+  - cs-gpio: A gpio specifier that specifies the gpio line used as
+    the slave select line by the spi controller. The format of the gpio
+    specifier depends on the gpio controller.
+
+  - samsung,spi-feedback-delay: The sampling phase shift to be applied on the
+    miso line (to account for any lag in the miso line). The following are the
+    valid values.
+
+      - 0: No phase shift.
+      - 1: 90 degree phase shift sampling.
+      - 2: 180 degree phase shift sampling.
+      - 3: 270 degree phase shift sampling.
+
+Aliases:
+
+- All the SPI controller nodes should be represented in the aliases node using
+  the following format 'spi{n}' where n is a unique number for the alias.
+
+
+Example:
+
+- SoC Specific Portion:
+
+	spi_0: spi@12d20000 {
+		compatible = "samsung,exynos4210-spi";
+		reg = <0x12d20000 0x100>;
+		interrupts = <0 66 0>;
+		tx-dma-channel = <&pdma0 5>;
+		rx-dma-channel = <&pdma0 4>;
+	};
+
+- Board Specific Portion:
+
+	spi_0: spi@12d20000 {
+		#address-cells = <1>;
+		#size-cells = <0>;
+		gpios = <&gpa2 4 2 3 0>,
+			<&gpa2 6 2 3 0>,
+			<&gpa2 7 2 3 0>;
+
+		w25q80bw@0 {
+			#address-cells = <1>;
+			#size-cells = <1>;
+			compatible = "w25x80";
+			reg = <0>;
+			spi-max-frequency = <10000>;
+
+			controller-data {
+				cs-gpio = <&gpa2 5 1 0 3>;
+				samsung,spi-feedback-delay = <0>;
+			};
+
+			partition@0 {
+				label = "U-Boot";
+				reg = <0x0 0x40000>;
+				read-only;
+			};
+
+			partition@40000 {
+				label = "Kernel";
+				reg = <0x40000 0xc0000>;
+			};
+		};
+	};