hello Wiser.Kuo,
you may refer to kernel initial messages, check all mounted serial ports,
for example,
$ dmesg | grep THS
you may access L4T sources packages for public release sources, you may check device tree settings for the mappings.
for example,
$L4T_Sources/r32.4.3/Linux_for_Tegra/source/public/hardware/nvidia/soc/t19x/kernel-dts/tegra194-soc/tegra194-soc-uart.dtsi
please also check similar discussion thread, Topic 125337 for reference.
thanks