Do you want to know where the definitions of this macros for i386 and x86_64 platform are? Yes? Then you would try cscope as usually. But it shows nothing relevant. You might also try to grep whole sources, but with no reliable output. It's not that easy.
Try to generate preprocessor output by -E switch and it will show you, that you should take a look into asm/io.h (i.e. include/asm-arch/io.h) and … what you see? BUILDIO for i386 and __OUT* macros for x86_64. Ugly. Sometimes, preprocessor output might be useful :).