dt-bindings: interrupt-controller: Add binding for NXP INTMUX interrupt multiplexer

This patch adds the DT bindings for the NXP INTMUX interrupt multiplexer
for i.MX8 family SoCs.
Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200117060653.27485-2-qiangqing.zhang@nxp.com

Documentation/devicetree/bindings/interrupt-controller/fsl,intmux.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/interrupt-controller/fsl,intmux.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Freescale INTMUX interrupt multiplexer
+
+maintainers:
+  - Joakim Zhang <qiangqing.zhang@nxp.com>
+
+properties:
+  compatible:
+    const: fsl,imx-intmux
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    minItems: 1
+    maxItems: 8
+    description: |
+      Should contain the parent interrupt lines (up to 8) used to multiplex
+      the input interrupts.
+
+  interrupt-controller: true
+
+  '#interrupt-cells':
+    const: 2
+    description: |
+      The 1st cell is hw interrupt number, the 2nd cell is channel index.
+
+  clocks:
+    description: ipg clock.
+
+  clock-names:
+    const: ipg
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - interrupt-controller
+  - '#interrupt-cells'
+  - clocks
+  - clock-names
+
+additionalProperties: false
+
+examples:
+  - |
+    interrupt-controller@37400000 {
+        compatible = "fsl,imx-intmux";
+        reg = <0x37400000 0x1000>;
+        interrupts = <0 16 4>,
+                     <0 17 4>,
+                     <0 18 4>,
+                     <0 19 4>,
+                     <0 20 4>,
+                     <0 21 4>,
+                     <0 22 4>,
+                     <0 23 4>;
+        interrupt-controller;
+        interrupt-parent = <&gic>;
+        #interrupt-cells = <2>;
+        clocks = <&clk>;
+        clock-names = "ipg";
+    };