There is an exposed paddle under the ADIN1300 package, and two keepout areas adjacent to the paddle on the package, what are they for?
The package has a standard exposed paddle, which should be soldered to the board for thermal reasons, ideally the solder pattern will have a full via array for best thermal performance.
The extra exposed strips seen above and below the exposed padded are exposed bus bars, they are connected to internal voltages, so should not be grounded. Take note that there should be no vias directly underneath these areas and should be treated as keep-out areas. They do not need to be soldered down.
More information, please go to page 78 of the ADIN1300 Datasheet, under the PCB Layout Recommendations Section.