How to reference a specific nvme partition for efibootmgr command?

I am trying to create an entry in nvram to boot an os of my choice. I have the xxxxxxxxx.efi file for it ready and placed in the second partition that is 32 bit FAT formatted for EFI and also contains my Windows and other OS loaders.

I have understood the syntax for referring to a HDD and its partitions as sda1, sda2 etc. so that I can type /dev/sda2 for eg. But with nvme I am not sure.

I have a single such nvme sdd in the only M2 slot on motherboard. How to address the second partition in it for efibootmgr command?