Getting called function from LLVM's machine instruction

Is there a way to get called function from a Machine Instruction?

Right now I'm identifying if the Machine Instruction is a function call or not as below:

     for (MachineBasicBlock &MBB : MF) {
      for (MachineInstr &MI : MBB) {
        if (MI.getDesc().isCall()) {
             //Function Call
        }
      }
  

I tried to follow this http://lists.llvm.org/pipermail/llvm-dev/2015-July/088100.html, but I'm getting isSymbol() as false in all cases.

Note: I'm interested only in direct calls(function pointers are ignored).