I can’t answer all of it (I don’t know what might be using the UART), but any “ttyTHS#” with the same “#” in “ttyS#” is the same UART controller hardware, but with different drivers. The “ttyTHS#” uses DMA, the “ttyS#” does not use DMA.
To see more you might look at:
find /sys -name '*uart*'
In the case of the “devices” subdirectory the UART will be named along with a controller address (plus “.serial” appended). I see “./devices/3110000.serial/tty/ttyTHS1/uartclk”, so ttyTHS1 is from the controller at address 0x3110000.
If I go to the TRM I find address 0x03110000 is associated with “UARTB”. So I can’t tell you what the UART is being used for, but it is “UARTB” in both “/sys” and the TRM.
If you want to see device tree settings, then I see this after extracting the running system’s device tree:
reg = <0x0 0x3110000 0x0 0x40>;
dmas = <0x19 0x9 0x19 0x9>;
interrupts = <0x0 0x71 0x4>;
reg-shift = <0x2>;
compatible = "nvidia,tegra186-hsuart";
clock-names = "serial", "parent";
reset-names = "serial";
nvidia,adjust-baud-rates = <0x1c200 0x1c200 0x64>;
clocks = <0xd 0x38 0xd 0x10d>;
resets = <0xd 0x30>;
nvidia,memory-clients = <0xe>;
status = "okay";
phandle = <0x81>;
#stream-id-cells = <0x1>;
dma-names = "rx", "tx";
linux,phandle = <0x81>;