ARM: ixp4xx: Add DT bindings

This adds initial device tree bindings for the IXP4xx machines.
This time I tried something wild and crazy and try to make proper
JSON-style YAML bindings for the top level.

Cc: devicetree@vger.kernel.org
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/arm/intel-ixp4xx.yaml

+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/arm/intel-ixp4xx.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Intel IXP4xx Device Tree Bindings
+
+maintainers:
+  - Linus Walleij <linus.walleij@linaro.org>
+
+properties:
+  compatible:
+    oneOf:
+      - items:
+          - enum:
+              - linksys,nslu2
+          - const: intel,ixp42x
+      - items:
+          - enum:
+              - gateworks,gw2358
+          - const: intel,ixp43x

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/arm/intel-ixp4xx.yaml
 F:	Documentation/devicetree/bindings/gpio/intel,ixp4xx-gpio.txt
 F:	Documentation/devicetree/bindings/interrupt-controller/intel,ixp4xx-interrupt.yaml
 F:	Documentation/devicetree/bindings/timer/intel,ixp4xx-timer.yaml