a2 platform is somewhat complex and usual .vkp patch method is absolutely and completely useless, because there is no fixed offsets anymore in phone flash chip.
everything placed in filesystem.
there is some kind of "bootloader" (called semcboot) which find and load pcore.cxc (actually, gathering it from pages) and runs it.
pcore that setup mmu,filesystem,etc and load
phone_acc.cxc - firmware for access subsystem
phone_app.cxc - firmware for application subsystem.
if required, pcore loads and run fota.cxc - to upgrade firmware.
mostly, users require to patch application firmware,cause it is one, which interface with users.
each .cxc is protected with rsa signature and funny checksum algorithm.
rsa signature of cxc is only checked on product domain phones and ignored on factory/r&d/ta phones.
so, to "patch" a2 phone user need:
1. a2 phone NOT in product (red) state (or semcboot should be patched properly)
2. get phone_app.cxc
3. patch phone_app.cxc
4. resign phone_app.cxc
5. upload phone_app.cxc back to phone.
as you can see, it is not enough to simple select .vkp and press "write script"

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