The kernels shipped with this build the 4.4 and mainline do support dynamic enabling of devices via borrowing of_overlays from Raspberry PI.
Since the 0.6.27 release all devices exposed on pins are disabled (except SPIDF).
You can easily enable these devices from command line if needed.
You can check the names of all devices here: https://github.com/ayufan-rock64/linux-kernel/blob/release-4.4/arch/arm64/boot/dts/rockchip/rk3328.dtsi, when confronted with pinout you might enable additional UARTs, ethernet interfaces, etc.
The extra ethernet interface is accessible on Pi-P5+ Bus which you can access with https://www.pine64.org/?product=rock64-stereo-audio-dac-add-on-board.
To enable it execute this command as root:
enable_dtoverlay eth1 ethernet@ff550000 okayThis will enable eth1 till next reboot. If you want to make it permamently consider adding this line to /etc/rc.local or other file that is executed on boot.
Contribute here to add information about different devices that might be interesting for the users: SPI, I2C, UART, GPIOs.