Have you tried after booting SD Card Linux the following commands?
# insmod /lib/modules/3.8.7-yocto-standard/kernel/drivers/usb/serial/pl2303.ko
# modprobe pl2303
and connect USB-Serial device?
Have you tried after booting SD Card Linux the following commands?
# insmod /lib/modules/3.8.7-yocto-standard/kernel/drivers/usb/serial/pl2303.ko
# modprobe pl2303
and connect USB-Serial device?