Upgrade Partition Image

Enter Bootloader Mode

While device is running normally, connect device's download port with
PC through Type-A to Tyep-C USB cable, then run this command on device
terminal or debug console:

   sudo systemctl reboot bootloader


Check Bootloader

Open windows terminal (PowerShell), navigate to the location of
Android Platform Tools, then run ".\fastboot.exe devices"

If the device is in the bootloader mode, fastboot will show a detected
device:

   PS D:\path\to\platform-tools> .\fastboot.exe devices
   xxxxxxxx         fastboot

If fastboot shows nothing, please check driver installation and usb
cable.

Download Partition Image

Usage: fastboot.exe flash "partition name" "path to image"

For example:

   .\fastboot.exe flash boot D:\path\to\boot.img

   .\fastboot.exe flash dtbo D:\path\to\dtbo.img

   # reboot device after download.
   .\fastboot.exe reboot

Notice: Download wrong file will cause system failure, so check before
download. Seek help first if don't understand. Don't act blindly.