You will need a service which maps the device node to a serial interface - we typically recommend ser2net.
Always use the /dev/serial/by-id/ path and not the device-node name because the node can enumerate as ttyUSB1 or ttyUSB0 depending on local configuration but the /dev/serial/by-id/ path does not change.
Something like:
# UART1 - nearest power connector - current kernel console.
6080:telnet:0:/dev/serial/by-id/usb-FTDI_TTL232RG-VREG1V8_FTXODY29-if00-port0:115200 8DATABITS NONE 1STOPBIT banner LOCAL
This allows the connection_command to be "telnet localhost 6080" and this can be tested locally.
{% set connection_list = ['uart0'] %}
{% set connection_tags = {'uart0': ['primary', 'telnet']} %}
{% set connection_commands = {'uart0': 'telnet localhost 7105'} %}
/etc/ser2net.conf needs to be modified on the worker if you want to use localhost. (This is expected because the DUT USB serial cable is plugged into the worker in most cases, so that the /dev/serial/by-id/ path exists on the worker.)