Documentation: admin-guide: add earlycon documentation for RISC-V

Kernels booting on RISC-V can specify "earlycon" with no options on
the Linux command line, and the generic DT earlycon support will query
the "chosen/stdout-path" property (if present) to determine which
early console device to use.  Document this appropriately in the
admin-guide.

Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Andreas Schwab <schwab@suse.de>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index edf65dad250b05ffe43b74ac20ca9224f2ea4b94..fd69e7f8ef797d79126c92d1b13f58df01614277 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -988,6 +988,10 @@
                        chosen node or the ACPI SPCR table if supported by
                        the platform.
 
+                       [RISCV] When used with no options, the early
+                       console is determined by the stdout-path
+                       property in the device tree's chosen node.
+
                cdns,<addr>[,options]
                        Start an early, polled-mode console on a Cadence
                        (xuartps) serial port at the specified address. Only