usb: add MediaTek USB3 DRD driver

This patch adds support for the MediaTek USB3 DRD controller,
its host side is based on xHCI, this driver supports device mode
and host mode.

Acked-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/drivers/usb/mtu3/mtu3_dr.h b/drivers/usb/mtu3/mtu3_dr.h
new file mode 100644
index 0000000..ec0e50c
--- /dev/null
+++ b/drivers/usb/mtu3/mtu3_dr.h
@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * mtu3_dr.h - dual role switch and host glue layer header
+ *
+ * Copyright (C) 2016 MediaTek Inc.
+ *
+ * Author: Chunfeng Yun <chunfeng.yun@mediatek.com>
+ */
+
+#ifndef _MTU3_DR_H_
+#define _MTU3_DR_H_
+
+#if IS_ENABLED(CONFIG_USB_MTU3_HOST)
+
+int ssusb_host_init(struct ssusb_mtk *ssusb);
+void ssusb_host_exit(struct ssusb_mtk *ssusb);
+
+#else
+
+static inline int ssusb_host_init(struct ssusb_mtk *ssusb)
+{
+	return 0;
+}
+
+static inline void ssusb_host_exit(struct ssusb_mtk *ssusb)
+{}
+
+#endif
+
+#if IS_ENABLED(CONFIG_USB_MTU3_GADGET)
+int ssusb_gadget_init(struct ssusb_mtk *ssusb);
+void ssusb_gadget_exit(struct ssusb_mtk *ssusb);
+irqreturn_t mtu3_irq(int irq, void *data);
+#else
+static inline int ssusb_gadget_init(struct ssusb_mtk *ssusb)
+{
+	return 0;
+}
+
+static inline void ssusb_gadget_exit(struct ssusb_mtk *ssusb)
+{}
+
+static inline irqreturn_t mtu3_irq(int irq, void *data)
+{
+	return IRQ_NONE;
+}
+#endif
+
+void ssusb_set_force_mode(struct ssusb_mtk *ssusb,
+			  enum mtu3_dr_force_mode mode);
+
+#endif		/* _MTU3_DR_H_ */