Yes @RFSpecialist, CSI RS resource are mapped per SSB.
Not related to CSI RS Port.
I am talking about resource allocation for CSI RS.
For example 1 CSI Port with 1 SSB configuration we need 4 npz resource required in one RB
nzp resources are configured as csi-rs ports. So when you see a csi-rs port with 8 ports, like in the example that I posted above, this is for csi-rs ports. It is not for a specific SSB but for all SSBs and for al PDSCH transmissions. Those CSI-RS ports are the radiating elements, virtual antenna elements of the gNodeB.
This is the most important picture to understand what csi-rs ports are. How layers are mapped to csi-rs ports using precoding matrix:
http://www.sharetechnote.com/html/5G/5G_CSI_RS_Codebook.html
Although for gNB with MIMO beamforming feature, csi RS port number is generally at least 2, 4 or above up to 32 for PMI report. But there is still practical purpose for port number is 1. For example, for OFDMA multi user mode without beamforming or without explicit beamforming, but gNB still need the CSI report from UE: CQI full band or subband report to schedule multiple user share all prb. This is also open the possibility for number of RB is less than the total PRB because not necessarily all user report full BWP CQI.