The tutorial is intended for those rolling their own boards out of an Arduino-based prototype, but it will work in any situation where you need multiple connections to a single set of UART pins.

You can’t make use of all of these at once, but with up to four different connections wired to a single pin you can carve out ... the Raspberry Pi’s one-and-a-half UART interface has long ...

Toshiba Electronics Europe has launched three new dual-supply bus transceivers to manage UART or SPI interfaces.