usb: dwc3: add Realtek DHC RTD SoC dwc3 glue layer driver

Realtek DHC RTD SoCs integrate dwc3 IP and has some customizations to
support different generations of SoCs.

The RTD1619b subclass SoC only supports USB 2.0 from dwc3. The driver
can set a maximum speed to support this. Add role switching function,
that can switch USB roles through other drivers, or switch USB roles
through user space through set /sys/class/usb_role/.
Signed-off-by: Stanley Chang <stanley_chang@realtek.com>
Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/20230826031028.1892-1-stanley_chang@realtek.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc3/Kconfig

@@ -178,4 +178,15 @@ config USB_DWC3_OCTEON
 	  Only the host mode is currently supported.
 	  Say 'Y' or 'M' here if you have one such device.
 
+config USB_DWC3_RTK
+	tristate "Realtek DWC3 Platform Driver"
+	depends on OF && ARCH_REALTEK
+	default USB_DWC3
+	select USB_ROLE_SWITCH
+	help
+	  RTK DHC RTD SoCs with DesignWare Core USB3 IP inside,
+	  and IP Core configured for USB 2.0 and USB 3.0 in host
+	  or dual-role mode.
+	  Say 'Y' or 'M' if you have such device.
+
 endif

drivers/usb/dwc3/Makefile

@@ -55,3 +55,4 @@ obj-$(CONFIG_USB_DWC3_QCOM)		+= dwc3-qcom.o
 obj-$(CONFIG_USB_DWC3_IMX8MP)		+= dwc3-imx8mp.o
 obj-$(CONFIG_USB_DWC3_XILINX)		+= dwc3-xilinx.o
 obj-$(CONFIG_USB_DWC3_OCTEON)		+= dwc3-octeon.o
+obj-$(CONFIG_USB_DWC3_RTK)		+= dwc3-rtk.o