If you are looking for specific technical documentation or hardware replacements, you can find resources through the following types of platforms:
Since these boards are available as spare parts, users can replace a water-damaged or "dead" board entirely with a new E7A_MB_PCB_V3 unit. Where to Find More Information e7a mb pcb v3 link
Locating specific capacitors or diodes that may have failed. If you are looking for specific technical documentation
The E7A motherboard is composed of several critical sub-systems necessary for smartphone operation: e7a mb pcb v3 link
E7A MB PCB V3 Wiring Diagram - Printed Circuit Board - Scribd
This is the primary ribbon cable "link" that connects the motherboard to the sub-board (charging port and speaker area).