Clarify impact of BIOS settings on T480 ports

docs/admin/hardware.rst

@@ -80,3 +80,12 @@ The instructions below assume the use of a Linux-based computer for the creation
 - Plug the USB into the T480 and boot it, pressing **F12** on startup. Select the USB's listing in the boot menu.
 
 - Follow the on-screen instructions to update the BIOS, including any mandatory reboots. Note that the instructions may refer to an update CD instead of your update USB.
+
+USB-C ports
+~~~~~~~~~~~
+If you intend to use USB-C ports, please note that our recommended BIOS settings will disable dual USB-C/Thunderbolt ports (recognizable by the Thunderbolt logo next to the port). The T480 includes two USB-C ports, `specified <https://www.lenovo.com/us/en/laptops/thinkpad/thinkpad-t-series/ThinkPad-T480/p/22TP2TT4800>`__ as follows:
+
+- 1 x USB 3.1 Gen 1 Type-C (Power Delivery, DisplayPort, Data transfer)
+- 1 x USB 3.1 Gen 2 Type-C / Intel Thunderbolt 3 (Power Delivery, DisplayPort, Data transfer)
+
+The first of these ports will continue to function as a USB-C port. After disabling Thunderbolt, the second port can no longer be used for Thunderbolt or for USB-C data transfer, but it can still be used for power delivery (i.e. to plug in your AC adapter). If you are unsure about the features of your laptop's USB-C ports, or if you are using a different make or model, please consult the technical specifications of your laptop for further information.