dt-bindings: reset: Add a binding for the RPi Firmware reset controller

The firmware running on the RPi VideoCore can be used to reset and
initialize HW controlled by the firmware.

Reviewed-by: Florian Fainelli <[e-mail]>
Signed-off-by: Nicolas Saenz Julienne <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/devicetree/bindings/arm/bcm/raspberrypi,bcm2835-firmware.yaml

···
       - compatible
       - "#clock-cells"
 
+  reset:
+    type: object
+
+    properties:
+      compatible:
+        const: raspberrypi,firmware-reset
+
+      "#reset-cells":
+        const: 1
+        description: >
+          The argument is the ID of the firmware reset line to affect.
+
+    required:
+      - compatible
+      - "#reset-cells"
+
     additionalProperties: false
 
 required:
···
         firmware_clocks: clocks {
             compatible = "raspberrypi,firmware-clocks";
             #clock-cells = <1>;
+        };
+
+        reset: reset {
+            compatible = "raspberrypi,firmware-reset";
+            #reset-cells = <1>;
         };
     };
 ...

include/dt-bindings/reset/raspberrypi,firmware-reset.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2020 Nicolas Saenz Julienne
+ * Author: Nicolas Saenz Julienne <[e-mail]>
+ */
+
+#ifndef _DT_BINDINGS_RASPBERRYPI_FIRMWARE_RESET_H
+#define _DT_BINDINGS_RASPBERRYPI_FIRMWARE_RESET_H
+
+#define RASPBERRYPI_FIRMWARE_RESET_ID_USB	0
+#define RASPBERRYPI_FIRMWARE_RESET_NUM_IDS	1
+
+#endif