The term 'UART1' is not a term conventionally used in Linux. I think you are asking how to find the device node associated with the device's driver. For that to happen, there must be a driver for the serial hardware. Are you sure this has occurred? If so, it may have left a record of its findings in a system log file. On a desktop or server host, you could usually find this information in the output of dmesg, and/or /var/log/messages. In either case, it s probably easiest to find the information using a simple visual scan of the logs; they are generally not really large. The useful info tends to be populated at boot time.