Serial ports are pretty easy to make work if you have the driver.
PL2303 works well and is usually embedded in USB hubs, USB gps etc.
You need to figure out the kernel version of your tablet.
in ADB shell.
Aslo you should figure out the exact telechips cpu in your tablet.
In my ROM, MalaRom, there is a big collection of modules fitting "126.96.36.199-tcc" kernel, compiled for telechips 9200 cpu.
If it fits yours, you can download my rom at http://www.michel-lange.net/tcc
Unzip the archive. In the folder DriverPack you will find a tar ball with all the modules.
Otherwise it is not so difficult to compile the modules from the telechips kernel sources.
You can find them here: