If you look at the 3.8.13 tinycore patched kernel source in linux-3.8.13-patched/drivers/tty, you can see various moxa files.
if you look at the kernel config using "make menuconfig" you can enable device drivers --> character devices --> non-standard serial port support as follows: [*] Non-standard serial port support
...
< > Cyclades async mux support (NEW)
<M> Moxa Intellio support
<M> Moxa SmartIO support v. 2.0
..and then recompile the kernel and see if things work.