dt-bindings: mailbox: Convert imx mu to json-schema

Convert the i.MX MU binding to DT schema format using json-schema
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/mailbox/fsl,mu.txt

-NXP i.MX Messaging Unit (MU)
---------------------------------------------------------------------
-
-The Messaging Unit module enables two processors within the SoC to
-communicate and coordinate by passing messages (e.g. data, status
-and control) through the MU interface. The MU also provides the ability
-for one processor to signal the other processor using interrupts.
-
-Because the MU manages the messaging between processors, the MU uses
-different clocks (from each side of the different peripheral buses).
-Therefore, the MU must synchronize the accesses from one side to the
-other. The MU accomplishes synchronization using two sets of matching
-registers (Processor A-facing, Processor B-facing).
-
-Messaging Unit Device Node:
-=============================
-
-Required properties:
--------------------
-- compatible :	should be "fsl,<chip>-mu", the supported chips include
-		imx6sx, imx7s, imx8qxp, imx8qm.
-		The "fsl,imx6sx-mu" compatible is seen as generic and should
-		be included together with SoC specific compatible.
-		There is a version 1.0 MU on imx7ulp, use "fsl,imx7ulp-mu"
-		compatible to support it.
-		To communicate with i.MX8 SCU, "fsl,imx8-mu-scu" could be
-		used for fast IPC
-- reg :		Should contain the registers location and length
-- interrupts :	Interrupt number. The interrupt specifier format depends
-		on the interrupt controller parent.
-- #mbox-cells:  Must be 2.
-			  <&phandle type channel>
-			    phandle   : Label name of controller
-			    type      : Channel type
-			    channel   : Channel number
-
-		This MU support 4 type of unidirectional channels, each type
-		has 4 channels. A total of 16 channels. Following types are
-		supported:
-		0 - TX channel with 32bit transmit register and IRQ transmit
-		acknowledgment support.
-		1 - RX channel with 32bit receive register and IRQ support
-		2 - TX doorbell channel. Without own register and no ACK support.
-		3 - RX doorbell channel.
-
-Optional properties:
--------------------
-- clocks :	phandle to the input clock.
-- fsl,mu-side-b : Should be set for side B MU.
-
-Examples:
---------
-lsio_mu0: mailbox@5d1b0000 {
-	compatible = "fsl,imx8qxp-mu", "fsl,imx6sx-mu";
-	reg = <0x0 0x5d1b0000 0x0 0x10000>;
-	interrupts = <GIC_SPI 176 IRQ_TYPE_LEVEL_HIGH>;
-	#mbox-cells = <2>;
-};

Documentation/devicetree/bindings/mailbox/fsl,mu.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mailbox/fsl,mu.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NXP i.MX Messaging Unit (MU)
+
+maintainers:
+  - Dong Aisheng <aisheng.dong@nxp.com>
+
+description: |
+  The Messaging Unit module enables two processors within the SoC to
+  communicate and coordinate by passing messages (e.g. data, status
+  and control) through the MU interface. The MU also provides the ability
+  for one processor to signal the other processor using interrupts.
+
+  Because the MU manages the messaging between processors, the MU uses
+  different clocks (from each side of the different peripheral buses).
+  Therefore, the MU must synchronize the accesses from one side to the
+  other. The MU accomplishes synchronization using two sets of matching
+  registers (Processor A-facing, Processor B-facing).
+
+properties:
+  compatible:
+    oneOf:
+      - const: fsl,imx6sx-mu
+      - const: fsl,imx7ulp-mu
+      - const: fsl,imx8-mu-scu
+      - items:
+          - enum:
+            - fsl,imx7s-mu
+            - fsl,imx8mq-mu
+            - fsl,imx8mm-mu
+            - fsl,imx8mn-mu
+            - fsl,imx8mp-mu
+            - fsl,imx8qxp-mu
+          - const: fsl,imx6sx-mu
+      - description: To communicate with i.MX8 SCU with fast IPC
+        items:
+          - const: fsl,imx8qxp-mu
+          - const: fsl,imx8-mu-scu
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  "#mbox-cells":
+    description: |
+      <&phandle type channel>
+      phandle   : Label name of controller
+      type      : Channel type
+      channel   : Channel number
+
+      This MU support 4 type of unidirectional channels, each type
+      has 4 channels. A total of 16 channels. Following types are
+      supported:
+      0 - TX channel with 32bit transmit register and IRQ transmit
+          acknowledgment support.
+      1 - RX channel with 32bit receive register and IRQ support
+      2 - TX doorbell channel. Without own register and no ACK support.
+      3 - RX doorbell channel.
+    const: 2
+
+  clocks:
+    maxItems: 1
+
+  fsl,mu-side-b:
+    description: boolean, if present, means it is for side B MU.
+    type: boolean
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - "#mbox-cells"
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+
+    mailbox@5d1b0000 {
+        compatible = "fsl,imx8qxp-mu", "fsl,imx6sx-mu";
+        reg = <0x5d1b0000 0x10000>;
+        interrupts = <GIC_SPI 176 IRQ_TYPE_LEVEL_HIGH>;
+        #mbox-cells = <2>;
+    };