Finally I got it compiled.
You can use now the usb2serial converters which uses the cp210x chipset.
the cp210x.tar.gz includes the obects and scripts to load/unload the driver
the cp210x_src.tar.gz includes the src which can be compiled by copying the tarball to the usr_src/ directory of the firmeware source tree.
Please, can you compile kernel modules for USB-serial: pl2303 or ftdi_sio adaptors?