dt-bindings: spi: Add hpe gxp spi

Add support for the HPE GXP SPI Controller.

Signed-off-by: Nick Hawkins <nick.hawkins@hpe.com>

doc/device-tree-bindings/spi/hpe,gxp-spi.yaml

@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/spi/hpe,gxp-spi.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: HPE GXP SPI Controller
+
+maintainers:
+  - Nick Hawkins <nick.hawkins@hpe.com>
+  - Jean-Marie Verdun <verdun@hpe.com>
+
+allOf:
+  - $ref: "spi-controller.yaml#"
+
+properties:
+  compatible:
+    const: mikrotik,rb4xx-spi
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    spi@c00000200{
+          compatible = "hpe,gxp-spi";
+          reg = <0xc0000200 0x80>;
+          #address-cells = <1>;
+          #size-cells = <0>;
+    };
+