hello oliver30sgx,
according to TX2 TRM, the maximum baud rate is 12.5Mbps.
please also access Tegra X2 (Parker Series SoC) Technical Reference Manual, and check the [UNIVERSAL ASYNCHRONOUS RECEIVER/TRANSMITTER (UART)] chapter.
please also refer to Jetson TX2 Series Software Features for the uart speeds.
you could also refer to UART registers in the Technical Reference Manual
thanks