knxd is a linux tool that can be used as router/gateway to talk to devices on a KNX bus. This add-on is providing the knxd daemon which you can use to create a KNX/IP gateway utilising TPUART or USB bus adapters from your home installation. So basically it can turn UART/USB interfaces into KNX IP-interfaces which you then can use in HomeAssistant or to program your KNX devices via ETS over ethernet. For more details see https://github.com/knxd/knxd.
See documentation