dt-bindings: interrupt-controller: Add nuvoton, wpcm450-aic

The WPCM450 AIC ("Advanced Interrupt Controller") is the interrupt
controller found in the Nuvoton WPCM450 SoC and other Winbond/Nuvoton
SoCs.
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210406120921.2484986-4-j.neuschaefer@gmx.net

Documentation/devicetree/bindings/interrupt-controller/nuvoton,wpcm450-aic.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/interrupt-controller/nuvoton,wpcm450-aic.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Nuvoton WPCM450 Advanced Interrupt Controller bindings
+
+maintainers:
+  - Jonathan Neuschäfer <j.neuschaefer@gmx.net>
+
+properties:
+  '#interrupt-cells':
+    const: 2
+
+  compatible:
+    const: nuvoton,wpcm450-aic
+
+  interrupt-controller: true
+
+  reg:
+    maxItems: 1
+
+additionalProperties: false
+
+required:
+  - '#interrupt-cells'
+  - compatible
+  - reg
+  - interrupt-controller
+
+examples:
+  - |
+    aic: interrupt-controller@b8002000 {
+        compatible = "nuvoton,wpcm450-aic";
+        reg = <0xb8002000 0x1000>;
+        interrupt-controller;
+        #interrupt-cells = <2>;
+    };