Hi Nimish,
lsusb returns this:
Bus 002 Device 021: ID 0403:6011 Future Technology Devices
International, Ltd FT4232H Quad HS USB-UART/FIFO IC
I had seen this note earlier, and thought I don't need to do anything
since product id was recognized fine. But, may be I need to something.
Let me check.
You will need to add a rule; lsusb just reads the device info,
it has nothing to do with drivers being loaded.
I believe the FTDI tech note discusses how to create a rule a
multi-channel device like the FT4232H - since you want the
ftdi_sio driver to create four /dev/ttyUSBx nodes.
Cheers,
Dave