dt-bindings: interrupt-controller: Add LS7A PCH LPC

Loongson 7A series PCH contains an LPC controller with an interrupt
controller.

Add the device tree binding for the interrupt controller.

Signed-off-by: Icenowy Zheng <zhengxingda@iscas.ac.cn>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20260321092032.3502701-4-zhengxingda@iscas.ac.cn

Documentation/devicetree/bindings/interrupt-controller/loongson,pch-lpc.yaml

@@ -0,0 +1,52 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/interrupt-controller/loongson,pch-lpc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Loongson PCH LPC Controller
+
+maintainers:
+  - Jiaxun Yang <jiaxun.yang@flygoat.com>
+
+description:
+  This interrupt controller is found in the Loongson LS7A family of PCH for
+  accepting interrupts sent by LPC-connected peripherals and signalling PIC
+  via a single interrupt line when interrupts are available.
+
+properties:
+  compatible:
+    const: loongson,ls7a-lpc
+
+  reg:
+    maxItems: 1
+
+  interrupt-controller: true
+
+  interrupts:
+    maxItems: 1
+
+  '#interrupt-cells':
+    const: 2
+
+required:
+  - compatible
+  - reg
+  - interrupt-controller
+  - interrupts
+  - '#interrupt-cells'
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    lpc: interrupt-controller@10002000 {
+      compatible = "loongson,ls7a-lpc";
+      reg = <0x10002000 0x400>;
+      interrupt-controller;
+      #interrupt-cells = <2>;
+      interrupt-parent = <&pic>;
+      interrupts = <19 IRQ_TYPE_LEVEL_HIGH>;
+    };
+...