dt-bindings: misc: ge-achc: Convert to DT schema format

Convert the binding to DT schema format. Also update the binding
to fix shortcomings

 * Add "nxp,kinetis-k20" fallback compatible
 * add programming SPI interface and reset GPIO
 * add main clock
 * add voltage supplies
 * drop spi-max-frequency from required properties,
   driver will setup max. frequency
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20210802172309.164365-2-sebastian.reichel@collabora.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/misc/ge-achc.txt

-* GE Healthcare USB Management Controller
-
-A device which handles data aquisition from compatible USB based peripherals.
-SPI is used for device management.
-
-Note: This device does not expose the peripherals as USB devices.
-
-Required properties:
-
-- compatible : Should be "ge,achc"
-
-Required SPI properties:
-
-- reg : Should be address of the device chip select within
-  the controller.
-
-- spi-max-frequency : Maximum SPI clocking speed of device in Hz, should be
-  1MHz for the GE ACHC.
-
-Example:
-
-spidev0: spi@0 {
-	compatible = "ge,achc";
-	reg = <0>;
-	spi-max-frequency = <1000000>;
-};

Documentation/devicetree/bindings/misc/ge-achc.yaml

+# SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
+# Copyright (C) 2021 GE Inc.
+# Copyright (C) 2021 Collabora Ltd.
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/misc/ge-achc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: GE Healthcare USB Management Controller
+
+description: |
+  A device which handles data acquisition from compatible USB based peripherals.
+  SPI is used for device management.
+
+  Note: This device does not expose the peripherals as USB devices.
+
+maintainers:
+  - Sebastian Reichel <sre@kernel.org>
+
+properties:
+  compatible:
+    items:
+      - const: ge,achc
+      - const: nxp,kinetis-k20
+
+  clocks:
+    maxItems: 1
+
+  vdd-supply:
+    description: Digital power supply regulator on VDD pin
+
+  vdda-supply:
+    description: Analog power supply regulator on VDDA pin
+
+  reg:
+    items:
+      - description: Control interface
+      - description: Firmware programming interface
+
+  reset-gpios:
+    description: GPIO used for hardware reset.
+    maxItems: 1
+
+required:
+  - compatible
+  - clocks
+  - reg
+  - reset-gpios
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        spi@1 {
+            compatible = "ge,achc", "nxp,kinetis-k20";
+            reg = <1>, <0>;
+            clocks = <&achc_24M>;
+            reset-gpios = <&gpio3 6 GPIO_ACTIVE_LOW>;
+        };
+    };