Hello Simone,
Mellanox RDMA supports ARM64 arch'.
The link below is referring to the latest driver release notes, on page 7 you may see the table that lists the supported platforms and operating systems.
http://www.mellanox.com/related-docs/prod_software/Mellanox_OFED_Linux_Release_Notes_3_0-1_0_1.pdf
Kind Regards,
Einav Ezra