SERCOM - Support for "Single-Wire Half-Duplex" UART

I found one comment in the Atmel SAMD21 spec says that the SERCOM module supports "single-wire half-duplex configuration" when acting as a UART. I can't find any more detail about how to do it. Does the uart class in the core support this? Is there any example? If it is not supported, can it be added?

Start by checking whether the core's UART class supports the SERCOM single-wire half-duplex mode described in the SAMD21 specification. The issue does not name files or tests, and it leaves open whether support or an example is missing; clarify which gap exists before defining what done looks like.

Written by the indexing model from the issue text.