dt-bindings: net: add marvell usb to mdio bindings

Describe how the USB to MDIO controller can optionally use device tree
bindings to reference attached devices such as switches.
Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/marvell,mvusb.yaml

+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/net/marvell,mvusb.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Marvell USB to MDIO Controller
+
+maintainers:
+  - Tobias Waldekranz <tobias@waldekranz.com>
+
+description: |+
+  This controller is mounted on development boards for Marvell's Link Street
+  family of Ethernet switches. It allows you to configure the switch's registers
+  using the standard MDIO interface.
+
+  Since the device is connected over USB, there is no strict requirement of
+  having a device tree representation of the device. But in order to use it with
+  the mv88e6xxx driver, you need a device tree node in which to place the switch
+  definition.
+
+allOf:
+  - $ref: "mdio.yaml#"
+
+properties:
+  compatible:
+    const: usb1286,1fa4
+  reg:
+    maxItems: 1
+    description: The USB port number on the host controller
+
+required:
+  - compatible
+  - reg
+  - "#address-cells"
+  - "#size-cells"
+
+examples:
+  - |
+    /* USB host controller */
+    &usb1 {
+            mvusb: mdio@1 {
+                    compatible = "usb1286,1fa4";
+                    reg = <1>;
+                    #address-cells = <1>;
+                    #size-cells = <0>;
+            };
+    };
+
+    /* MV88E6390X devboard */
+    &mvusb {
+            switch@0 {
+                    compatible = "marvell,mv88e6190";
+                    status = "ok";
+                    reg = <0x0>;
+
+                    ports {
+                            /* Port definitions */
+                    };
+
+                    mdio {
+                            /* PHY definitions */
+                    };
+            };
+    };

MAINTAINERS

@@ -10106,6 +10106,12 @@ M:	Nicolas Pitre <nico@fluxnic.net>
 S:	Odd Fixes
 F:	drivers/mmc/host/mvsdio.*
 
+MARVELL USB MDIO CONTROLLER DRIVER
+M:	Tobias Waldekranz <tobias@waldekranz.com>
+L:	netdev@vger.kernel.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/net/marvell,mvusb.yaml
+
 MARVELL XENON MMC/SD/SDIO HOST CONTROLLER DRIVER
 M:	Hu Ziji <huziji@marvell.com>
 L:	linux-mmc@vger.kernel.org