dt-bindings: dmaengine: Add binding for Actions Semi Owl SoCs

Add devicetree binding for Actions Semi Owl SoCs DMA controller.
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Documentation/devicetree/bindings/dma/owl-dma.txt

+* Actions Semi Owl SoCs DMA controller
+
+This binding follows the generic DMA bindings defined in dma.txt.
+
+Required properties:
+- compatible: Should be "actions,s900-dma".
+- reg: Should contain DMA registers location and length.
+- interrupts: Should contain 4 interrupts shared by all channel.
+- #dma-cells: Must be <1>. Used to represent the number of integer
+              cells in the dmas property of client device.
+- dma-channels: Physical channels supported.
+- dma-requests: Number of DMA request signals supported by the controller.
+                Refer to Documentation/devicetree/bindings/dma/dma.txt
+- clocks: Phandle and Specifier of the clock feeding the DMA controller.
+
+Example:
+
+Controller:
+                dma: dma-controller@e0260000 {
+                        compatible = "actions,s900-dma";
+                        reg = <0x0 0xe0260000 0x0 0x1000>;
+                        interrupts = <GIC_SPI 57 IRQ_TYPE_LEVEL_HIGH>,
+                                     <GIC_SPI 58 IRQ_TYPE_LEVEL_HIGH>,
+                                     <GIC_SPI 59 IRQ_TYPE_LEVEL_HIGH>,
+                                     <GIC_SPI 60 IRQ_TYPE_LEVEL_HIGH>;
+                        #dma-cells = <1>;
+                        dma-channels = <12>;
+                        dma-requests = <46>;
+                        clocks = <&clock CLK_DMAC>;
+                };
+
+Client:
+
+DMA clients connected to the Actions Semi Owl SoCs DMA controller must
+use the format described in the dma.txt file, using a two-cell specifier
+for each channel.
+
+The two cells in order are:
+1. A phandle pointing to the DMA controller.
+2. The channel id.
+
+uart5: serial@e012a000 {
+        ...
+        dma-names = "tx", "rx";
+        dmas = <&dma 26>, <&dma 27>;
+        ...
+};