irqchip: ixp4xx: Add DT bindings

This adds device tree bindings for the IXP4xx interrupt
controller. It's a standard 2-cell controller.

Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: devicetree@vger.kernel.org
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/interrupt-controller/intel,ixp4xx-interrupt.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# Copyright 2018 Linaro Ltd.
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/interrupt/intel-ixp4xx-interrupt.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: Intel IXP4xx XScale Networking Processors Interrupt Controller
+
+maintainers:
+  - Linus Walleij <linus.walleij@linaro.org>
+
+description: |
+  This interrupt controller is found in the Intel IXP4xx processors.
+  Some processors have 32 interrupts, some have up to 64 interrupts.
+  The exact number of interrupts is determined from the compatible
+  string.
+
+  The distinct IXP4xx families with different interrupt controller
+  variations are IXP42x, IXP43x, IXP45x and IXP46x. Those four
+  families were the only ones to reach the developer and consumer
+  market.
+
+properties:
+  compatible:
+    items:
+      - enum:
+        - intel,ixp42x-interrupt
+        - intel,ixp43x-interrupt
+        - intel,ixp45x-interrupt
+        - intel,ixp46x-interrupt
+
+  reg:
+    maxItems: 1
+
+  interrupt-controller: true
+
+  '#interrupt-cells':
+    const: 2
+
+required:
+  - compatible
+  - reg
+  - interrupt-controller
+  - '#interrupt-cells'
+
+examples:
+  - |
+    intcon: interrupt-controller@c8003000 {
+        compatible = "intel,ixp43x-interrupt";
+        reg = <0xc8003000 0x100>;
+        interrupt-controller;
+        #interrupt-cells = <2>;
+    };

MAINTAINERS

@@ -1690,6 +1690,7 @@ M:	Imre Kaloz <kaloz@openwrt.org>
 M:	Krzysztof Halasa <khalasa@piap.pl>
 L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
 S:	Maintained
+F:	Documentation/devicetree/bindings/interrupt-controller/intel,ixp4xx-interrupt.yaml
 F:	arch/arm/mach-ixp4xx/
 F:	drivers/clocksource/timer-ixp4xx.c
 F:	drivers/gpio/gpio-ixp4xx.c