Documentation/contributing: Update sign-off procedure

The Linux kernel recently updated the wording of their sign-off
procedure, changing the ambiguous "real name" requirement to "a known
identity" and dropping "no pseudonyms". Anonymous contributions remain
uncommittable [1]. As discussed in the April 19, 2023 leadership
meeting, update our policy to go along with Linux and flashrom (who also
updated their policy).

[1] Linux kernel commit d4563201f3
(Documentation: simplify and clarify DCO contribution example language)

Change-Id: Ie676334f7c1509524adcb8dbb78495fb4da35ede
Signed-off-by: Nicholas Chin <nic.c3.14@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/74851
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <patrick@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
diff --git a/Documentation/contributing/gerrit_guidelines.md b/Documentation/contributing/gerrit_guidelines.md
index b6ebc0f..c6f5fbf 100644
--- a/Documentation/contributing/gerrit_guidelines.md
+++ b/Documentation/contributing/gerrit_guidelines.md
@@ -141,9 +141,11 @@
 to your commit message.  Patches without a Signed-off-by should not be
 pushed to gerrit, and will be rejected by coreboot's CI system.
 
-You must use your real name in the Signed-off-by line. Patches without
-an associated real name cannot be committed! Refer to [this LKML thread]
-and the [SCO-Linux disputes] for the rationale behind the DCO.
+You must use a known identity in the Signed-off-by line. Anonymous
+contributions cannot be committed! This can be anything sufficient to
+identify and contact the source of a contribution, such as your name or
+an established alias/nickname. Refer to [this LKML thread] and the
+[SCO-Linux disputes] for the rationale behind the DCO.
 
 Developer's Certificate of Origin 1.1