Cypress devices will use the Broadcom devices facility(for historical reasons..)

 This patch add support for Bluetooth Cypress chipsets:
RPi 0w  - Cypress CYW43143 - 802.11 b/g/n, Bluetooth  - BCM43143
RPi 3a+ - Cypress CYW43455 - 802.11ac, Bluetooth         - BCM43455
RPi 3b+ - Cypress CYW43438 - 802.11 b/g/n, Bluetooth - BCM43438
RPi 4b   - Cypress CYW43455 - 802.11ac, Bluetooth         - BCM43455

This Wireless chips, use the broadcomm facilities for historical reason( they were Broadomm until 2016.. )
They use a UART_3WIRE, instead of the usual 4 wire, they also lack flow control..
They don't need t set speed on initialization, so on init its there a condition to only do setuartpeed() if its other devices..

This patch as zero compatibility problems with other devices, and its self contained..
They are present, at least, in RaspBerryPi devices, but they are also present in a lot of broader devices..