doc: describe who's -p, -r, and -t options

* doc/coreutils.texi (who invocation):

1 files changed, 18 insertions, 0 deletions

diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 155ba8d7b..44df6b3e5 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -12710,6 +12710,24 @@ automatic dial-up internet access.
 @opindex --heading
 Print a line of column headings.
 
+@item -p
+@itemx --process
+@opindex -p
+@opindex --process
+List active processes spawned by init.
+
+@item -r
+@itemx --runlevel
+@opindex -r
+@opindex --runlevel
+Print the current (and maybe previous) run-level of the init process.
+
+@item -t
+@itemx --time
+@opindex -t
+@opindex --time
+Print last system clock change.
+
 @item -w
 @itemx -T
 @itemx --mesg