Thank you for contacting the Intel community.
Please check if the information at the following link helps:
If you scroll down there is some information for Serial-over-LAN and Linux
I know this website, I just want to know about the serial hardware specifications on the NUC.
I'm talking about serial port on the NUC ie ttyS0 ttyS1 etc... I want to know the speed that I can support.
After further investigation here is the information we could find for you.
In this case to accomplish this task we will need a cable (or makes one) that the port is RS-232 compliant, so it should work just like any other RS-232 port.
You can get the cables from here: http://www.gorite.com/intel-nuc-products/intel-nuc-cables
Bit rates commonly supported include 75, 110, 300, 1200, 2400, 4800, 9600, 19200, 38400, 57600 and 115200 bit/s
I hope this can be useful for you.