mount_nfs.8: Document the new "mountport" NFS mount option

Commit 0e8a36a2ab adds a new NFS mount
option called mountport.

This patch for the man page documents this new NFS mount option.

This is a content change.

(cherry picked from commit 91a74536a1)

sbin/mount_nfs/mount_nfs.8

@@ -27,7 +27,7 @@
 .\"
 .\"	@(#)mount_nfs.8	8.3 (Berkeley) 3/29/95
 .\"
-.Dd June 14, 2023
+.Dd November 29, 2024
 .Dt MOUNT_NFS 8
 .Os
 .Sh NAME
@@ -198,6 +198,16 @@ This should be used for mounts on old servers that cannot handle a
 group list size of 16, as specified in RFC 1057.
 Try 8, if users in a lot of groups cannot get response from the mount
 point.
+.It Cm mountport Ns = Ns Aq Ar value
+Specify the port number to be used to communicate with
+.Xr mountd 8
+on the NFS server.
+This option allows an NFSv2 or NFSv3 mount to be done without
+the need to run the
+.Xr rpcbind 8
+service.
+This option is meaningless for an NFSv4 mount, since NFSv4
+does not use the Mount protocol.
 .It Cm mntudp
 Force the mount protocol to use UDP transport, even for TCP NFS mounts.
 (Necessary for some old
@@ -673,6 +683,7 @@ Same as
 .Xr mount 8 ,
 .Xr nfsd 8 ,
 .Xr nfsiod 8 ,
+.Xr rpcbind 8 ,
 .Xr rpc.tlsclntd 8 ,
 .Xr showmount 8
 .Sh HISTORY