Documentation: kernel-parameters: Add DEVNAME:0.0 format for serial ports

Document the console option for DEVNAME:0.0 style addressing for serial
ports.

Suggested-by: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Dhruva Gole <d-gole@ti.com>
Link: https://lore.kernel.org/r/20240327110021.59793-8-tony@atomide.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 623fce7d5fcd0c4392432908e21aaba5134e3aa0..ecf94382981fb5ba79b0d919a850a84f49cb2d0b 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -785,6 +785,25 @@
                        Documentation/networking/netconsole.rst for an
                        alternative.
 
+               <DEVNAME>:<n>.<n>[,options]
+                       Use the specified serial port on the serial core bus.
+                       The addressing uses DEVNAME of the physical serial port
+                       device, followed by the serial core controller instance,
+                       and the serial port instance. The options are the same
+                       as documented for the ttyS addressing above.
+
+                       The mapping of the serial ports to the tty instances
+                       can be viewed with:
+
+                       $ ls -d /sys/bus/serial-base/devices/*:*.*/tty/*
+                       /sys/bus/serial-base/devices/00:04:0.0/tty/ttyS0
+
+                       In the above example, the console can be addressed with
+                       console=00:04:0.0. Note that a console addressed this
+                       way will only get added when the related device driver
+                       is ready. The use of an earlycon parameter in addition to
+                       the console may be desired for console output early on.
+
                uart[8250],io,<addr>[,options]
                uart[8250],mmio,<addr>[,options]
                uart[8250],mmio16,<addr>[,options]