console,uart,tty的关联关系_uart 驱动怎么和 console 联系上

config VT
bool "Virtual terminal" if EMBEDDED
select INPUT
default y if !VIOCONS
---help---
    If you say Y here, you will get support for terminal devices with
    display and keyboard devices. These are called "virtual" because you
    can run several virtual terminals (also called virtual consoles) on
    one physical terminal. This is rather useful, for example one
    virtual terminal can collect system messages and warnings, another
    one can be used for a text-mode user session, and a third could run
    an X session, all in parallel. Switching between virtual terminals
    is done with certain key combinations, usually Alt-<function key>.

    The setterm command ("man setterm") can be used to change the
    properties (such as colors or beeping) of a virtual terminal. The
    man page console_codes(4) ("man console_codes") contains the special
    character sequences that can be used to change those properties
    directly. The fonts used on virtual terminals can be changed with
    the setfont ("man setfont") command and the key bindings are defined
    with the loadkeys ("man loadkeys") command.

    You need at least one virtual terminal device in order to make use
    of your keyboard and monitor. Therefore, only people configuring an
    embedded system would want to say N here in order to save some
    memory; the only way to log into such a system is then via a serial
    or network connection.

    If unsure, say Y, or else you won't be able to do much with your new
    shiny Linux system :-)

config VT_CONSOLE
bool "Support for console on virtual terminal" if EMBEDDED
depends on VT
default y
---help---
    The system console is the device which receives all kernel messages
    and warnings and which allows logins in single user mode. If you
    answer Y here, a virtual terminal (the device used to interact with
    a physical terminal) can be used as system console. This is the most
    common mode of operations, so you should say Y here unless you want
    the kernel messages be output only to a serial port (in which case
    you should say Y to "Console on serial port", below).

    If you do say Y here, by default the currently visible virtual
    terminal (/dev/tty0) will be used as system console. You can change
    that with a kernel command line option such as "console=tty3" which
    would use the third virtual terminal as system console. (Try "man
    bootparam" or see the documentation of your boot loader (lilo or
    loadlin) about how to pass options to the kernel at boot time.)

    If unsure, say Y.

config SERIAL_8250_CONSOLE
bool "Console on 8250/16550 and compatible serial port"
depends on SERIAL_8250=y
select SERIAL_CORE_CONSOLE
---help---
    If you say Y here, it will be possible to use a serial port as the
    system console (the system console is the device which receives all
    kernel messages and warnings and which allows logins in single user
    mode). This could be useful if some terminal or printer is connected
    to that serial port.

    Even if you say Y here, the currently visible virtual console
    (/dev/tty0) will still be used as the system console by default, but
    you can alter that using a kernel command line option such as
    "console=ttyS1". (Try "man bootparam" or see the documentation of
    your boot loader (grub or lilo or loadlin) about how to pass options
    to the kernel at boot time.)

    If you don't have a VGA card installed and you say Y here, the
    kernel will automatically use the first serial line, /dev/ttyS0, as
    system console.

    If unsure, say N.