BQ76PL455A-Q1: COMMH/L Lines

Part Number:BQ76PL455A-Q1

Hi, 

In the datasheet for the BQ76PL455A-Q1 it recommends including TVS diodes on either side of the communication line for IC's on the same PCB, the centre of these diodes is both shown as grounded as in the picture below, should these be grounded the the GND of their individual IC's or should both be grounded the the lowest IC out of the 2?

Thanks,

Alex