dt-bindings: interrupt-controller: Add support for Microchip LAN966x OIC

The Microchip LAN966x outband interrupt controller (OIC) maps the
internal interrupt sources of the LAN966x device to an external
interrupt.
When the LAN966x device is used as a PCI device, the external interrupt
is routed to the PCI interrupt.
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20240614173232.1184015-22-herve.codina@bootlin.com

Documentation/devicetree/bindings/interrupt-controller/microchip,lan966x-oic.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/interrupt-controller/microchip,lan966x-oic.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Microchip LAN966x outband interrupt controller
+
+maintainers:
+  - Herve Codina <herve.codina@bootlin.com>
+
+allOf:
+  - $ref: /schemas/interrupt-controller.yaml#
+
+description: |
+  The Microchip LAN966x outband interrupt controller (OIC) maps the internal
+  interrupt sources of the LAN966x device to an external interrupt.
+  When the LAN966x device is used as a PCI device, the external interrupt is
+  routed to the PCI interrupt.
+
+properties:
+  compatible:
+    const: microchip,lan966x-oic
+
+  '#interrupt-cells':
+    const: 2
+
+  interrupt-controller: true
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+required:
+  - compatible
+  - '#interrupt-cells'
+  - interrupt-controller
+  - interrupts
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    interrupt-controller@e00c0120 {
+        compatible = "microchip,lan966x-oic";
+        reg = <0xe00c0120 0x190>;
+        #interrupt-cells = <2>;
+        interrupt-controller;
+        interrupts = <0>;
+        interrupt-parent = <&intc>;
+    };
+...