As per the official notification Minimum Educational Qualification:
For admission to the examination, a candidate must have –
(a) obtained a degree in Engineering from a University incorporated by an Act of the Central or State Legislature in India or
other Educational Institutions established by an Act of Parliament or declared to be deemed as Universities under Section 3 of
the University Grants Commission Act, 1956; or
(b) passed Sections A and B of the Institution Examinations of the Institution of Engineers (India); or
(c) obtained a degree/diploma in Engineering from such foreign University/College/Institution and under such conditions
as may be recognised by the Government for the purpose from time to time, or
(d) passed Graduate Membership Examination of the Institution of Electronics and Telecommunication Engineers (India);
or
(e) passed Associate Membership Examination Parts II and III/Sections A and B of the Aeronautical Society of India; or
(f) passed Graduate Membership Examination of the Institution of Electronics and Radio Engineers, London held after
November, 1959

Which simply means any enigneering graduate can apply for the exam. But you can only give exam in following 4 discipline-

• Mechanical Engineering
• Civil Engineering
• Electronics & Telecommunication Engineering
• Electrical Engineering