spi: add bindings for microchip mpfs spi

Add device tree bindings for the {q,}spi controller on
the Microchip PolarFire SoC.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20220117110755.3433142-7-conor.dooley@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/spi/microchip,mpfs-spi.yaml

@@ -0,0 +1,52 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/spi/microchip,mpfs-spi.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Microchip MPFS {Q,}SPI Controller Device Tree Bindings
+
+maintainers:
+  - Conor Dooley <conor.dooley@microchip.com>
+
+allOf:
+  - $ref: spi-controller.yaml#
+
+properties:
+  compatible:
+    enum:
+      - microchip,mpfs-spi
+      - microchip,mpfs-qspi
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clock-names:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include "dt-bindings/clock/microchip,mpfs-clock.h"
+    spi@20108000 {
+        compatible = "microchip,mpfs-spi";
+        reg = <0x20108000 0x1000>;
+        clocks = <&clkcfg CLK_SPI0>;
+        interrupt-parent = <&plic>;
+        interrupts = <54>;
+        spi-max-frequency = <25000000>;
+    };
+...