charging 3 rockpro64 from single source

[rpt312]

I am very new to rockpro64. I am looking for charging 3 rockpro64 from a single source. Below are the things I have checked:
1. PoE using switch - I checked the documentation and the home page, but there is no mention of PoE.
2. Charging from USB - I have no idea and tried my best to find it but don't find enough information.
3. Charging from usb3 - I have no idea and tried my best to find it but don't find enough information.

It would be very helpful if someone have any information that can help me.

[dukla2000]

Simple, just solder your own 12v cables and use a power supply like this.
 
(I make no recommendation about this fleabay vendor, it is purely a link to illustrate the type of PSU I use for my RockPRO64.)