drivers: udc: add SOF Kconfig option and SOF event helper

Add helper to handle SOF interrupts/events and new Kconfig option to
disable SOF interrupt.

Signed-off-by: Johann Fischer <johann.fischer@nordicsemi.no>

drivers/usb/udc/Kconfig

@@ -42,6 +42,12 @@ config UDC_BUF_FORCE_NOCACHE
 	  Place the buffer pools in the nocache memory region if the driver
 	  cannot handle buffers in cached memory.
 
+config UDC_ENABLE_SOF
+	bool "SOF interrupt processing"
+	help
+	  Enabled SoF interrupts can cause a very high CPU load on high-speed
+	  controllers because the interrupt rate would be 125 µs.
+
 config UDC_WORKQUEUE
 	bool "Use a dedicate work queue for UDC drivers"
 	help

drivers/usb/udc/udc_common.h

@@ -156,6 +156,29 @@ int udc_submit_event(const struct device *dev,
 int udc_submit_ep_event(const struct device *dev,
 			struct net_buf *const buf,
 			const int err);
+
+/**
+ * @brief Helper function to send UDC SOF event to a higher level.
+ *
+ * Type of this event is hardcoded to UDC_EVT_SOF.
+ *
+ * @param[in] dev    Pointer to device struct of the driver instance
+ */
+#if defined(CONFIG_UDC_ENABLE_SOF)
+static inline void udc_submit_sof_event(const struct device *dev)
+{
+	struct udc_data *data = dev->data;
+	struct udc_event drv_evt = {
+		.type = UDC_EVT_SOF,
+		.dev = dev,
+	};
+
+	(void)data->event_cb(dev, &drv_evt);
+}
+#else
+#define udc_submit_sof_event(dev) ARG_UNUSED(dev)
+#endif
+
 /**
  * @brief Helper function to enable endpoint.
  *