adding si3210 driver

adding si3210 driver

[Giuseppe Lippolis]

Hi All,
I have a router running linux (LEDE distribution) with an embedded 3G modem
and a POTS telephone interface.
The telephone interface uses the si3210 device interfaced with the uP
through an spi IF.
The si3210 ProSLIC integrates a subscriber line interface circuit (SLIC) and
is commonly found in several router with telephone functions.

Because I was unable to find a driver for the si3210, I'm now using the
spidev interface to control the device from the userspace. 

Now I'm thinking to add a spi protocol char driver for that device.

My first question is if make sense to do this; I see other similar tentative
never embedded in the mainstream:
https://github.com/stelhs/slic_tdm
https://github.com/opennetworklinux/linux-3.8.13/tree/master/drivers/tdm/lin
e_ctrl

Second question is: What class the driver belong to? (in which drivers/
subfolder shall I add the driver)?

Thanks for the support.
Bye.