driver to using platform-device. I got a reply, that it's not worth it now 
that IDE is slowly becoming obsolete, and the pata_platform serves the 
perpose perfectly well. I found this argument reasonable, I had the same 
doubt, just wanted to double-check. So, why do we now need a new legacy 
(a/drivers/ide/legacy/ide_platform.c) driver when a "modern" driver 
exists?

We don't *need* it but some people still want to use old IDE and the
author was willing to make it neatly compatible so that anything that
works with the pata_platform should be able to use the ide_platform
driver and vice versa. For the shorter term that can only be a good thing
- arch code doesn't need to care about which driver is used, end users
can pick and it doesn't end up adding new ties between code and old IDE.