This circumstance is most common with Cisco Nexus Series switches, where the switch’s hot air exhaust can be on the back or front.
As a result, port side intake denotes cold air entering the switch where the ports are located, whereas port side exhaust denotes hot air leaving the switch. Nexus switch lets you choose whether to intake from the front or the back.
• Front-to-back airflow is provided by this option, with vents aligned with the heated aisle (port-side exhaust). This option is appropriate for ToR deployments that require the fabric extender ports to be aligned with the server ports in a particular rack.
• Reversed-airflow fan: With ports aligned with the cold aisle, this alternative provides back-to-front airflow (port-side intake). This option is appropriate for network rack deployments that need the alignment of several network equipment ports.
I would say in most Data Centers I’ve built out or worked on, “port-side exhaust” is used for ToR deployments. The ports are facing the hot-air isle mainly because of where all the server ports are located. It just makes it easier for cable management. These would be your leaf switches. For the Spine, it would be the opposite airflow typically. These will have a “port-side intake” because they are facing the cold aisle and don’t need to face the hot-air aisle. Most of the time, your network equipment will be set up to accommodate this setup(always check).