[Help] [Unlock Bootloader] how to unlock bootloader of mt6580 device ?

m using Walton Primo GF4 ..... mt6580..... Lolipop 5.1......

i want to root it...... but bootloader is locked...... i tried all rooting software.....didnt worked :(
hang with "No Command" text in recovery mood... tell me... how to unlock bootloder