Proposal v2: identifying modems and mobile broadband cards

[Dan Williams]

Hi,

- An interface that has the "serial" capability acquires the 'modem'
capability if the serial interface is indeed known to have a modem on
the other side

- An interface with the 'modem' capability may also acquire the property
'modem.at_command_sets', which is a string array of supported command
sets, denoted by their abbreviated standards name. If the property is
present, it is assumed the modem supports rudimentary Hayes-compatible
AT commands.  The key may contain _one or more_ of the following values:

   a) IS-707-A  (for CDMA supporting cards)
   b) GSM-07-07  (for GSM supporting cards)
   c) GSM-07-05  (for GSM supporting cards)

Sound OK?

Dan