Understanding udev’s ID_PATH for USB devices

When plugging different peripherals into the same USB port, the udev ID_PATH reports slightly different values.

Peripheral A: platform-fe9c0000.xhci-usb-0:1:1.0
Peripheral B: platform-fe9c0000.xhci-usb-0:1:4.2

I’d like to understand the naming scheme and the difference in the trailing portion (1.0 vs 4.2). I’ve tried searching the udev documentation but didn’t have any luck. Is this explained/documented somewhere?

In case helpful/relevant, have collected the above on an RPi 4 running Debian Bookworm.