hello momo_chen,
all the logs were sending to UART2 (i.e. Debug UART) is reserve for kernel debug purpose.
according to the screenshot, that’s mb1 logs, you may also check Boot flow for reference.
FYI,
could you please follow-up this topic, Topic 160948, it shows some changes for disabling combined uart on Xavier,
please check this and try to apply the code to Xavier NX.
thanks