vCenter Licensing

Hi

Can someone help with me a vCenter licensing question.

We are about to P to V multiple infrastructures, and need to know if the vCenter licensing model purely works on the amount of processors you have across all your infrastructures.

for example:

Would i be allowed to use a single license that would cover 8 processors across 2 different air gaped infrastructures, installed twice. Or would i need to purchase 2x seperate vCenter licenses for 4 procs in each?

Thanks