Nexus 9364C entity tree

I am looking into integrating our N9K-C9364C switches into our management system. In particular, I need to find a way to link ports in ENTITY-MIB with interfaces identified by ifIndex... should be easy, right?

But this is how ports are numbered in ENTITY-MIB (just first four for brevity):

 5206 | port | 1 | Linecard-1 Port-1 (Linecard-1 Port-1) 5210 | port | 5 | Linecard-1 Port-5 (Linecard-1 Port-5) 5214 | port | 9 | Linecard-1 Port-9 (Linecard-1 Port-9) 5218 | port | 13 | Linecard-1 Port-13 (Linecard-1 Port-13) 

So Ethernet1/1 is Port-1, Ethernet1/2 is Port-5... Ethernet1/54 is Port-261.

What the ... ? Looks like I will need to special-case this. Or is there any logic to how Cisco dumps info into ENTITY-MIB entPhysicalTable?