Documentation/serial-console.txt: convert it to ReST markup

- Fix identation for the document title;
- use monotonic fonts for paths;
- use quote blocks where needed;
- adjust spaces to properly format paragraphs;
- use :menuselection: for the menu item;
- add it to the user book.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/serial-console.txt

-                       Linux Serial Console
+Linux Serial Console
+====================
 
 To use a serial port as console you need to compile the support into your
 kernel - by default it is not compiled in. For PC style serial ports
-it's the config option next to "Standard/generic (dumb) serial support".
+it's the config option next to menu option:
+
+:menuselection:`Character devices --> Serial drivers --> 8250/16550 and compatible serial support --> Console on 8250/16550 and compatible serial port`
+
 You must compile serial support into the kernel and not as a module.
 
 It is possible to specify multiple devices for console output. You can
 define a new kernel command line option to select which device(s) to
 use for console output.
 
-The format of this option is:
+The format of this option is::
 
 	console=device,options
 
@@ -28,11 +32,11 @@ The format of this option is:
 
 You can specify multiple console= options on the kernel command line.
 Output will appear on all of them. The last device will be used when
-you open /dev/console. So, for example:
+you open ``/dev/console``. So, for example::
 
 	console=ttyS1,9600 console=tty0
 
-defines that opening /dev/console will get you the current foreground
+defines that opening ``/dev/console`` will get you the current foreground
 virtual console, and kernel messages will appear on both the VGA
 console and the 2nd serial port (ttyS1 or COM2) at 9600 baud.
 
@@ -44,17 +48,17 @@ first looks for a VGA card and then for a serial port. So if you don't
 have a VGA card in your system the first serial port will automatically
 become the console.
 
-You will need to create a new device to use /dev/console. The official
-/dev/console is now character device 5,1.
+You will need to create a new device to use ``/dev/console``. The official
+``/dev/console`` is now character device 5,1.
 
 (You can also use a network device as a console.  See
-Documentation/networking/netconsole.txt for information on that.)
+``Documentation/networking/netconsole.txt`` for information on that.)
 
-Here's an example that will use /dev/ttyS1 (COM2) as the console.
+Here's an example that will use ``/dev/ttyS1`` (COM2) as the console.
 Replace the sample values as needed.
 
-1. Create /dev/console (real console) and /dev/tty0 (master virtual
-   console):
+1. Create ``/dev/console`` (real console) and ``/dev/tty0`` (master virtual
+   console)::
 
      cd /dev
      rm -f console tty0
@@ -63,42 +67,42 @@ Replace the sample values as needed.
 
 2. LILO can also take input from a serial device. This is a very
    useful option. To tell LILO to use the serial port:
-   In lilo.conf (global section): 
+   In lilo.conf (global section)::
 
      serial  = 1,9600n8 (ttyS1, 9600 bd, no parity, 8 bits)
 
 3. Adjust to kernel flags for the new kernel,
-   again in lilo.conf (kernel section)
+   again in lilo.conf (kernel section)::
 
      append = "console=ttyS1,9600"
 
 4. Make sure a getty runs on the serial port so that you can login to
    it once the system is done booting. This is done by adding a line
-   like this to /etc/inittab (exact syntax depends on your getty):
+   like this to ``/etc/inittab`` (exact syntax depends on your getty)::
 
      S1:23:respawn:/sbin/getty -L ttyS1 9600 vt100
 
-5. Init and /etc/ioctl.save
+5. Init and ``/etc/ioctl.save``
 
-   Sysvinit remembers its stty settings in a file in /etc, called
-   `/etc/ioctl.save'. REMOVE THIS FILE before using the serial
+   Sysvinit remembers its stty settings in a file in ``/etc``, called
+   ``/etc/ioctl.save``. REMOVE THIS FILE before using the serial
    console for the first time, because otherwise init will probably
    set the baudrate to 38400 (baudrate of the virtual console).
 
-6. /dev/console and X
+6. ``/dev/console`` and X
    Programs that want to do something with the virtual console usually
-   open /dev/console. If you have created the new /dev/console device,
+   open ``/dev/console``. If you have created the new ``/dev/console`` device,
    and your console is NOT the virtual console some programs will fail.
    Those are programs that want to access the VT interface, and use
-   /dev/console instead of /dev/tty0. Some of those programs are:
+   ``/dev/console instead of /dev/tty0``. Some of those programs are::
 
      Xfree86, svgalib, gpm, SVGATextMode
 
    It should be fixed in modern versions of these programs though.
 
-   Note that if you boot without a console= option (or with
-   console=/dev/tty0), /dev/console is the same as /dev/tty0. In that
-   case everything will still work.
+   Note that if you boot without a ``console=`` option (or with
+   ``console=/dev/tty0``), ``/dev/console`` is the same as ``/dev/tty0``.
+   In that case everything will still work.
 
 7. Thanks