Hi @gavinhans
There is a tool but for N9K: https://www.cisco.com/c/dam/en/us/td/docs/Website/datacenter/ISSUmatrix/index.html
Since the upgrade path is disruptive anyway, and the jump from 5.2.5 is HUGE, and since it will take forever to do cold upgrades, what I will do is schedule a full day upgrade window and: wipe the config, perform the upgrade to 8.2 directly (note there will be need for upgrade of FPGA as well) put the config back.
This way there will be a lot of time saved. Alternatively, you will have to go through cold disruptive upgrades:
5.2(5) -> 6.1(5a) -> 8.2(4)
You can find these details by looking at cold boot upgrade matrix:
https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus7000/sw/upgrade/guide/cisco_nexus7000_software_upgrade_and_downgrade_guide_8x.html
https://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/6_x/nx-os/upgrade/guide/b_Cisco_Nexus_7000_Series_NX-OS_Software_Upgrade_and_Downgrade_Guide_Release_6-x.html
Stay safe,
Sergiu
