See railway jobs are for 10+2 or graduates. Now there are no such specifications for most RRB examination except the JE examination. For JE examination you must have a Diploma in Engineering or BTech degree but for all the remaining you must have a graduate degree and it doesn't matter what subject it is.

** For Railways JOB you have to prepare it separately.

I hope this answer helps. All the very best for your future endeavors!