earlycon: 8250: Document kernel command line options

Document the expected behavior of kernel command lines of the forms:
    console=uart[8250],io|mmio|mmio32,<addr>[,options]
    console=uart[8250],<addr>[,options]
and
    earlycon=uart[8250],io|mmio|mmio32,<addr>[,options]
    earlycon=uart[8250],<addr>[,options]

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index 18142ee3c013..422ebea96a64 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -3471,12 +3471,13 @@ static int univ8250_console_setup(struct console *co, char *options)
  *      @options: ptr to option string from console command line
  *
  *      Only attempts to match console command lines of the form:
- *          console=uart<>,io|mmio|mmio32,<addr>,<options>
- *          console=uart<>,<addr>,options
+ *          console=uart[8250],io|mmio|mmio32,<addr>[,<options>]
+ *          console=uart[8250],0x<addr>[,<options>]
  *      This form is used to register an initial earlycon boot console and
  *      replace it with the serial8250_console at 8250 driver init.
  *
  *      Performs console setup for a match (as required by interface)
+ *      If no <options> are specified, then assume the h/w is already setup.
  *
  *      Returns 0 if console matches; otherwise non-zero to use default matching
  */