I suppose a copyright notice is appropriate to indicate the origins of the SD additions.
mmc.c is the only file with substancial changes so it should be enough with a notice there.
Index: linux-sd/drivers/mmc/mmc.c =================================================================== --- linux-sd/drivers/mmc/mmc.c (revision 141) +++ linux-sd/drivers/mmc/mmc.c (working copy) @@ -2,6 +2,8 @@ * linux/drivers/mmc/mmc.c * * Copyright (C) 2003-2004 Russell King, All Rights Reserved. + * SD support Copyright (C) 2004 Ian Molton, All Rights Reserved. + * SD support Copyright (C) 2005 Pierre Ossman, All Rights Reserved. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as
