dt-bindings: usb: generic: Add role-switch-default-mode binding

Add binding to configure the default role the controller
assumes is host mode when the usb role is USB_ROLE_NONE.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
CC: ShuFan Lee <shufan_lee@richtek.com>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Chunfeng Yun <chunfeng.yun@mediatek.com>
Cc: Yu Chen <chenyu56@huawei.com>
Cc: Felipe Balbi <balbi@kernel.org>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Jun Li <lijun.kernel@gmail.com>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Guillaume Gardet <Guillaume.Gardet@arm.com>
Cc: Jack Pham <jackp@codeaurora.org>
Cc: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Cc: linux-usb@vger.kernel.org
Cc: devicetree@vger.kernel.org
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Felipe Balbi <balbi@kernel.org>

Documentation/devicetree/bindings/usb/generic.txt

@@ -35,6 +35,12 @@ Optional properties:
 			the USB data role (USB host or USB device) for a given
 			USB connector, such as Type-C, Type-B(micro).
 			see connector/usb-connector.txt.
+ - role-switch-default-mode: indicating if usb-role-switch is enabled, the
+			device default operation mode of controller while usb
+			role is USB_ROLE_NONE. Valid arguments are "host" and
+			"peripheral". Defaults to "peripheral" if not
+			specified.
+
 
 This is an attribute to a USB controller such as: