What is the best approach for creating a portal hierarchy?
Lets make "Computer" as an example. "Computer" will be the Parent of all portals. The computer will have a sub-portal / child, such as “Laptop,” “Desktop,” and “Printers.” Then, for each child, he will also have another sub-portal / child, such as “HP Notebook”, “Lenovo Laptop” or “HP Desktop”, etc.

For each portal, it will look different. Some of the portal will share portlet and content from each other. For example, USB products will take portlets from IBM Desktop or Brothers Printers, which will take content from HP Laptop.
Any user of the Portal can access all of these portals without re-registering. This means that the user from HP Printers can access the HP Notebook PCs. Each Portal is a separate person, it will have its own domain. But on the backend, they exchange portlets and other resources.
Hope this makes sense.
What is the best way to do this?
Does this create a “portal instance”?
or should he be in the "Organization"?
Thanks in advance!