pmbootstrap bootimg_analyze -f boot.img 
[22:04:44] NOTE: You will be prompted for your sudo/doas password, so we can set up a chroot to extract and analyze your boot.img file
[22:04:46] (native) install file unpackbootimg
[22:04:47] WARNING: boot.img file seems to be invalid, but proceeding anyway (-f specified)
[22:04:47] Put these variables in the deviceinfo file of your device:

deviceinfo_kernel_cmdline="console=ttyS1,115200n8"
deviceinfo_generate_bootimg="true"
deviceinfo_bootimg_qcdt="true"
deviceinfo_bootimg_dtb_second="false"
deviceinfo_flash_pagesize="2048"
deviceinfo_bootimg_qcdt_type="sprd"
deviceinfo_flash_offset_base="0x00000000"
deviceinfo_flash_offset_kernel="0x00008000"
deviceinfo_flash_offset_ramdisk="0x01000000"
deviceinfo_flash_offset_second="0x00f00000"
deviceinfo_flash_offset_tags="0x00000100"

[22:04:47] NOTE: chroot is still active (use 'pmbootstrap shutdown' as necessary)
[22:04:47] DONE!