When port type 18 was removed, it was deduced that the code could go but its define has to stay because it is used in userspace. Share that knowledge by adding a comment about it. Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> Link: https://lore.kernel.org/r/20230922063642.4120-3-wsa+renesas@sang-engineering.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>