[U-Boot-Users] How can a file in directory "u-boot-1.1.4\include\configs" be included?

Hello guys

I'm a beginner at u-boot porting and have a question about how can a file in directory "u-boot-1.1.4\include\configs", say pxa255_idp.h, be included in the whole project? I just can not find any code line like "#include <pxa255_idp.h>". The question is easy for non-beginners but hard for me. Any advice is appreciated.