This selects whether you want to include the driver for the standard
serial ports. The standard answer is Y. People who might say N
here are those that are setting up dedicated Ethernet WWW/FTP
servers, or users that have one of the various bus mice instead of a
serial mouse and don't intend to use their machine's standard serial
port for anything.

To compile this driver as a module, choose M here: the
module will be called 8250.
[WARNING: Do not compile this driver as a module if you are using
non-standard serial ports, since the configuration information will
be lost when the driver is unloaded. This limitation may be lifted
in the future.]

BTW1: If you have a mouseman serial mouse which is not recognized by
the X window system, try running gpm first.

BTW2: If you intend to use a software modem (also called Winmodem)
under Linux, forget it. These modems are crippled and require
proprietary drivers which are only available under Windows.

Most people will say Y or M here, so that they can use serial mice,
modems and similar devices connecting to the standard serial ports.

source code:

drivers/tty/serial/8250/