dt-bindings: interrupt-controller: Convert csky,mpintc to DT schema

Convert the C-SKY Multi-processor interrupt controller binding to schema
format. It's a straight-forward conversion of the typical interrupt
controller.

Link: https://lore.kernel.org/r/20250505144640.1288458-1-robh@kernel.org
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>

Author: robherring

Documentation/devicetree/bindings/interrupt-controller/csky,mpintc.txt

@@ -0,0 +1,43 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/interrupt-controller/csky,mpintc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: C-SKY Multi-processors Interrupt Controller
+
+maintainers:
+  - Guo Ren <guoren@kernel.org>
+
+description: >
+  C-SKY Multi-processors Interrupt Controller is designed for ck807/ck810/ck860
+  SMP soc, and it also could be used in non-SMP system.
+
+  Interrupt number definition:
+    0-15  : software irq, and we use 15 as our IPI_IRQ.
+    16-31  : private  irq, and we use 16 as the co-processor timer.
+    31-1024: common irq for soc ip.
+
+properties:
+  compatible:
+    const: csky,mpintc
+
+  '#interrupt-cells':
+    const: 2
+
+  interrupt-controller: true
+
+required:
+  - compatible
+  - "#interrupt-cells"
+  - interrupt-controller
+
+additionalProperties: false
+
+examples:
+  - |
+    interrupt-controller {
+        compatible = "csky,mpintc";
+        #interrupt-cells = <2>;
+        interrupt-controller;
+    };