How to install subordinate CA certificate into keychain from Terminal? I'm a Windows engineer, setting up a Active Directory PKI, but know very little about Macs.  I'm aware of how to install root certificates into the system keychain using:

sudo security add-trusted-cert -d -r trustRoot -k \Library\Keychains\System.keychain rootca.crt

However, I'm not too clear on how to install a subordinate CA's certificate (that was issued by the root CA).

Do I simply use the exact same command, or would i use add-certificates instead?

What is the difference between the resultypes: trustRoot, trustAsRoot, unspecified?
Since the subordinate CA's certificate is already "trusted" due to the root CA's cert being in the System Roots, you just need to use the add-certificates command, specifying the System keychain.

sudo security add-certificates -k /Library/Keychains/System.keychain your_cert_file