dt-bindings: fsl: scu: add ocotp binding

NXP i.MX8QXP is an ARMv8 SoC with a Cortex-M4 core inside as
system controller(SCU), the ocotp controller is being controlled
by the SCU, so Linux need use RPC to SCU for ocotp handling. This
patch adds binding doc for i.MX8 SCU OCOTP driver.

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Anson Huang <anson.huang@nxp.com>
Cc: devicetree@vger.kernel.org
Reviewed-by: NRob Herring <robh@kernel.org>
Reviewed-by: NDong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: NPeng Fan <peng.fan@nxp.com>
Signed-off-by: NSrinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/arm/freescale/fsl,scu.txt

@@ -133,6 +133,18 @@ RTC bindings based on SCU Message Protocol
 Required properties:
 - compatible: should be "fsl,imx8qxp-sc-rtc";
 
+OCOTP bindings based on SCU Message Protocol
+------------------------------------------------------------
+Required properties:
+- compatible:		Should be "fsl,imx8qxp-scu-ocotp"
+- #address-cells:	Must be 1. Contains byte index
+- #size-cells:		Must be 1. Contains byte length
+
+Optional Child nodes:
+
+- Data cells of ocotp:
+  Detailed bindings are described in bindings/nvmem/nvmem.txt
+
 Example (imx8qxp):
 -------------
 aliases {
@@ -177,6 +189,16 @@ firmware {
 			...
 		};
 
+		ocotp: imx8qx-ocotp {
+			compatible = "fsl,imx8qxp-scu-ocotp";
+			#address-cells = <1>;
+			#size-cells = <1>;
+
+			fec_mac0: mac@2c4 {
+				reg = <0x2c4 8>;
+			};
+		};
+
 		pd: imx8qx-pd {
 			compatible = "fsl,imx8qxp-scu-pd", "fsl,scu-pd";
 			#power-domain-cells = <1>;