Excel table to json converter

I have a excel table with contains the following data: format:

mainheading:    
   subheading:
       mandatory:
         fieldname:
           type:
           description:
           function:
       optional:
          type
          description

      

again cycle repeats. Need to loop through that excel and required for

Need a optimum way to do it. can anyone help how to deal with this excel to json conversion