Hi, If you are referring to Berkeley, California...
I have several friends with school-age children in that city. What I have heard from them (which you should confirm directly with the district) is that the Berkeley Unified School District currently has a lottery-style approach to school assignment, in which parents list their top three choices and are assigned to one of them (which may or may not be the school closest to their home). The contact information for this district can be found on this page in SchoolFinder: http://www.education.com/schoolfinder/us/california/district/berkeley-unified-school-district/ Please do follow up with them to learn specifics about their enrollment policies, procedures and deadlines.
If you were referring to another Berkeley, or are looking into enrollment in a neighboring city or district, here is the main page of SchoolFinder where you can start your search: http://www.education.com/schoolfinder/
I'm also including below a link to some additional resources you may find helpful to your family. Good luck -- I hope all goes well in getting your child enrolled in school.