[PATCH v7 7/7] Documentation: kernel-parameters: Add DEVNAME:0.0 format for serial ports

[Tony Lindgren]

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

Suggested-by: Sebastian Reichel <sre@xxxxxxxxxx>
Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx>
---
 .../admin-guide/kernel-parameters.txt         | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
--- 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]
-- 
2.44.0