dt-bindings: interrupt-controller: Add Loongson EIOINTC

Add Loongson Extended I/O Interrupt controller binding with DT schema
format using json-schema.
Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/4369959615eda101e612c450b8974d76ce7e8821.1683279769.git.zhoubinbin@loongson.cn

Documentation/devicetree/bindings/interrupt-controller/loongson,eiointc.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/interrupt-controller/loongson,eiointc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Loongson Extended I/O Interrupt Controller
+
+maintainers:
+  - Binbin Zhou <zhoubinbin@loongson.cn>
+
+description: |
+  This interrupt controller is found on the Loongson-3 family chips and
+  Loongson-2K series chips and is used to distribute interrupts directly to
+  individual cores without forwarding them through the HT's interrupt line.
+
+allOf:
+  - $ref: /schemas/interrupt-controller.yaml#
+
+properties:
+  compatible:
+    enum:
+      - loongson,ls2k0500-eiointc
+      - loongson,ls2k2000-eiointc
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  interrupt-controller: true
+
+  '#interrupt-cells':
+    const: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - interrupt-controller
+  - '#interrupt-cells'
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    eiointc: interrupt-controller@1fe11600 {
+      compatible = "loongson,ls2k0500-eiointc";
+      reg = <0x1fe10000 0x10000>;
+
+      interrupt-controller;
+      #interrupt-cells = <1>;
+
+      interrupt-parent = <&cpuintc>;
+      interrupts = <3>;
+    };
+
+...