Rooted D6653 Stock 5.1.1 successfully. (long method)

:silly: (I had a TA backup of 5.0.2 stock rom before proceeding, and supersu 2.49 beta.zip).
followed steps like:
1. I updated My Z3 to 5.1.1
2. then unlocked my bootloader
3. flashed cm12.1 boot.img
4. booted into cwm recovery using cm12.1 boot.img
5. flashed supersu 2.49 beta.zip
6. reflashed the 5.1.1 kernel back using stock 5.1.1 ftf and flashtool ( only kernel dont reflash system!!!!!!!!! )
7. successfully booted into rooted stock rom.

FROM HERE BOOTLOADER LOCK WITH TA PARTITION BEGINS

8. run backup TA and restore previous TA Backup of 5.0.2 and reboot the phone( usb debugging must be enabled).
9. Now the phone is a locked bootloader with TA installed of 5.0.2 (partially compatible kernel but locked bootloader with TA and DRM keys)
10. reflash the 5.1.1 kernel back using stock 5.1.1 ftf and flashtool. ( only kernel dont reflash system!!!!!!!!! )
11. yipee.. you got a rooted 5.1.1 stock rom with locked bootloader.
You then can install XZ Dual recovery and can reflash supersu beta 2.49.zip if you face problem in mounting system R/w.
Finally Done. :laugh::laugh:

If you didnt had TA backup and are on locked bootloader then you can revert back to 5.0.2 , root it using kingroot, backup TA and then follow steps from post.