dt-bindings: spi: Convert spi-pxa2xx to json-schema

A straightforward conversion of the the spi-pxa2xx binding to DT schema
format using json-schema.
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
[robh: add unevaluatedProperties]
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/spi/marvell,mmp2-ssp.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright 2019,2020 Lubomir Rintel <lkundrak@v3.sk>
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/spi/marvell,mmp2-ssp.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: PXA2xx SSP SPI Controller bindings
+
+maintainers:
+  - Lubomir Rintel <lkundrak@v3.sk>
+
+allOf:
+  - $ref: spi-controller.yaml#
+
+properties:
+  compatible:
+    const: marvell,mmp2-ssp
+
+  interrupts:
+    maxItems: 1
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  ready-gpios:
+    description: |
+      GPIO used to signal a SPI master that the FIFO is filled and we're
+      ready to service a transfer. Only useful in slave mode.
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+
+dependencies:
+  ready-gpios: [ spi-slave ]
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/clock/marvell,mmp2.h>
+    spi@d4035000 {
+        compatible = "marvell,mmp2-ssp";
+        #address-cells = <1>;
+        #size-cells = <0>;
+        reg = <0xd4035000 0x1000>;
+        clocks = <&soc_clocks MMP2_CLK_SSP0>;
+        interrupts = <0>;
+    };
+
+...

Documentation/devicetree/bindings/spi/spi-pxa2xx.txt

-PXA2xx SSP SPI Controller
-
-Required properties:
-- compatible: Must be "marvell,mmp2-ssp".
-- reg: Offset and length of the device's register set.
-- interrupts: Should be the interrupt number.
-- clocks: Should contain a single entry describing the clock input.
-- #address-cells:  Number of cells required to define a chip select address.
-- #size-cells: Should be zero.
-
-Optional properties:
-- cs-gpios: list of GPIO chip selects. See the SPI bus bindings,
-  Documentation/devicetree/bindings/spi/spi-bus.txt
-- spi-slave: Empty property indicating the SPI controller is used in slave mode.
-- ready-gpios: GPIO used to signal a SPI master that the FIFO is filled
-  and we're ready to service a transfer. Only useful in slave mode.
-
-Child nodes represent devices on the SPI bus
-  See ../spi/spi-bus.txt
-
-Example:
-	ssp1: spi@d4035000 {
-		compatible = "marvell,mmp2-ssp";
-		reg = <0xd4035000 0x1000>;
-		clocks = <&soc_clocks MMP2_CLK_SSP0>;
-		interrupts = <0>;
-	};