powerpc/512x: add a device tree binding for LocalPlus Bus FIFO

Add a device tree binding for Freescale MPC512x LocalPlus Bus FIFO and
introduce the document describing that binding.

Signed-off-by: Alexander Popov <[e-mail]>
Signed-off-by: Anatolij Gustschin <[e-mail]>

Documentation/devicetree/bindings/powerpc/fsl/mpc512x_lpbfifo.txt

···
+Freescale MPC512x LocalPlus Bus FIFO (called SCLPC in the Reference Manual)
+
+Required properties:
+- compatible: should be "fsl,mpc512x-lpbfifo";
+- reg: should contain the offset and length of SCLPC register set;
+- interrupts: should contain the interrupt specifier for SCLPC; syntax of an
+    interrupt client node is described in interrupt-controller/interrupts.txt;
+- dmas: should contain the DMA specifier for SCLPC as described at
+    dma/dma.txt and dma/mpc512x-dma.txt;
+- dma-names: should be "rx-tx";
+
+Example:
+
+	sclpc@10100 {
+		compatible = "fsl,mpc512x-lpbfifo";
+		reg = <0x10100 0x50>;
+		interrupts = <7 0x8>;
+		dmas = <&dma0 26>;
+		dma-names = "rx-tx";
+	};
+

arch/powerpc/boot/dts/mpc5121.dtsi

···
 		#address-cells = <2>;
 		#size-cells = <1>;
 		reg = <0x80000020 0x40>;
-		interrupts = <7 0x8>;
 		ranges = <0x0 0x0 0xfc000000 0x04000000>;
 	};
 
···
 		/* LocalPlus controller */
 		lpc@10000 {
 			compatible = "fsl,mpc5121-lpc";
-			reg = <0x10000 0x200>;
+			reg = <0x10000 0x100>;
+		};
+
+		sclpc@10100 {
+			compatible = "fsl,mpc512x-lpbfifo";
+			reg = <0x10100 0x50>;
+			interrupts = <7 0x8>;
+			dmas = <&dma0 26>;
+			dma-names = "rx-tx";
 		};
 
 		pata@10200 {

arch/powerpc/boot/dts/mpc5125twr.dts

···
 			status = "disabled";
 		};
 
+		sclpc@10100 {
+			compatible = "fsl,mpc512x-lpbfifo";
+			reg = <0x10100 0x50>;
+			interrupts = <7 0x8>;
+			dmas = <&dma0 26>;
+			dma-names = "rx-tx";
+		};
+
 		// 5125 PSCs are not 52xx or 5121 PSC compatible
 		// PSC1 uart0 aka ttyPSC0
 		serial@11100 {
···
 			clock-names = "ipg";
 		};
 
-		dma@14000 {
+		dma0: dma@14000 {
 			compatible = "fsl,mpc5121-dma"; // BSP name: "mpc512x-dma2"
 			reg = <0x14000 0x1800>;
 			interrupts = <65 0x8>;
+			#dma-cells = <1>;
 		};
 	};
 };