usb: dwc3: glue: Add documentation

We're about to add more exported functions to be used inside glue
driver which will need more detailed documentation explaining how
they must be used. Let's also add documentation for the functions
already available.

Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Signed-off-by: Sven Peter <sven@kernel.org>
Link: https://patch.msgid.link/20251015-b4-aplpe-dwc3-v2-3-cbd65a2d511a@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: svenpeter42

drivers/usb/dwc3/glue.h

@@ -36,9 +36,36 @@ struct dwc3_probe_data {
 	struct dwc3_properties properties;
 };
 
+/**
+ * dwc3_core_probe - Initialize the core dwc3 driver
+ * @data: Initialization and configuration parameters for the controller
+ *
+ * Initializes the DesignWare USB3 core driver by setting up resources,
+ * registering interrupts, performing hardware setup, and preparing
+ * the controller for operation in the appropriate mode (host, gadget,
+ * or OTG). This is the main initialization function called by glue
+ * layer drivers to set up the core controller.
+ *
+ * Return: 0 on success, negative error code on failure
+ */
 int dwc3_core_probe(const struct dwc3_probe_data *data);
+
+/**
+ * dwc3_core_remove - Deinitialize and remove the core dwc3 driver
+ * @dwc: Pointer to DWC3 controller context
+ *
+ * Cleans up resources and disables the dwc3 core driver. This should be called
+ * during driver removal or when the glue layer needs to shut down the
+ * controller completely.
+ */
 void dwc3_core_remove(struct dwc3 *dwc);
 
+/*
+ * The following callbacks are provided for glue drivers to call from their
+ * own pm callbacks provided in struct dev_pm_ops. Glue drivers can perform
+ * platform-specific work before or after calling these functions and delegate
+ * the core suspend/resume operations to the core driver.
+ */
 int dwc3_runtime_suspend(struct dwc3 *dwc);
 int dwc3_runtime_resume(struct dwc3 *dwc);
 int dwc3_runtime_idle(struct dwc3 *dwc);