@NoviceNetworker
It is possible to set remote devices being managed by your main controller.
But first you need to make sure some setup is done:
1. Your main location with Controller has to have Public IP address. If the address is dynamic (not static) - you should use Dynamic DNS or some similar service to make sure the IP will be constantly updated
2. Make sure that port forwarding is set up properly in main location. Contoller is using specific ports to manage devices, update its firmware and so on. Make sure you have redirected those ports from WAN to your Controller's internal IP address. [UDP 19810, UDP 29810, TCP 29811, TCP 29812, TCP 29813, TCP 29814, TCP 29815, and TCP 29816]
3. Pre-prepare remote site's configuration in controller. Create remote site in your controller, configure there WiFi settings [SSID, Passwords and so on] - do all of this BEFORE you adopt your remote WiFi AP. When you will start the adoption, the controller will try to push Site's settings to AP, if those are not prepared, the local config of AP's settings will be lost and remote site (clients) will stop working.
Once you have done the steps above, you can access your remote AP's config page and go to: System [1] => Controller Settings [2]:
Enable the Cloud-Based Controller Management [3], update Controller's URL [4] and Save the changes [5].
In the URL section you can provide your Main location's IP address (if it's statis IP address) or web address (from DynDNS for example).
In my case I just simply deleted everything from URL field and placed the web address of my main location. Since the ports were redirected properly, it worked within a minute.
Once it's done, within few minutes, you should be able to find the EAP in your controller's device list as ready to adopt. Then proceed with it's adoption (choose site, provide device's login and password). The EAP will receive your remote site's settings (from point 3 of the list above).
For me, the EAP110 and ER605 are adopted and managed from different location than the controller and it works.
Keep in mind that since rest of your equipment are unmanaged (TP-Link switches) or are not TP-Link hardware (ISP's router), those will not be visible in the controller.
Hope it helps.