usb: core: hub: Create platform devices for onboard hubs in hub_probe()

Call onboard_hub_create/destroy_pdevs() from hub_probe/disconnect()
to create/destroy platform devices for onboard USB hubs that may be
connected to the hub. The onboard hubs must have nodes in the
device tree.

onboard_hub_create/destroy_pdevs() are NOPs unless
CONFIG_USB_ONBOARD_HUB=y/m.

Also add a field to struct usb_hub to keep track of the onboard hub
platform devices that are owned by the hub.

Reviewed-by: Douglas Anderson <[e-mail]>
Signed-off-by: Matthias Kaehlcke <[e-mail]>
Link: https://lore.kernel.org/r/20220630123445.v24.4.Ic9dd36078f9d803de82ca01a6700c58b8e4de27e@changeid
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/core/hub.c

···
 #include <linux/usb.h>
 #include <linux/usbdevice_fs.h>
 #include <linux/usb/hcd.h>
+#include <linux/usb/onboard_hub.h>
 #include <linux/usb/otg.h>
 #include <linux/usb/quirks.h>
 #include <linux/workqueue.h>
···
 	if (hub->quirk_disable_autosuspend)
 		usb_autopm_put_interface(intf);
 
+	onboard_hub_destroy_pdevs(&hub->onboard_hub_devs);
+
 	kref_put(&hub->kref, hub_release);
 }
 
···
 	INIT_DELAYED_WORK(&hub->leds, led_work);
 	INIT_DELAYED_WORK(&hub->init_work, NULL);
 	INIT_WORK(&hub->events, hub_event);
+	INIT_LIST_HEAD(&hub->onboard_hub_devs);
 	spin_lock_init(&hub->irq_urb_lock);
 	timer_setup(&hub->irq_urb_retry, hub_retry_irq_urb, 0);
 	usb_get_intf(intf);
···
 		usb_autopm_get_interface_no_resume(intf);
 	}
 
-	if (hub_configure(hub, &desc->endpoint[0].desc) >= 0)
+	if (hub_configure(hub, &desc->endpoint[0].desc) >= 0) {
+		onboard_hub_create_pdevs(hdev, &hub->onboard_hub_devs);
+
 		return 0;
+	}
 
 	hub_disconnect(intf);
 	return -ENODEV;

drivers/usb/core/hub.h

···
 	spinlock_t		irq_urb_lock;
 	struct timer_list	irq_urb_retry;
 	struct usb_port		**ports;
+	struct list_head        onboard_hub_devs;
 };
 
 /**