Is there an app note for migrating a design from AD9371?
The design of AD9371 is completely different from that of ADRV9009. You have to start from the beginning for bringing up ADRV9009.
The pinouts are near identical. Surely some customers have migrated AD9371 designs.
It is not possible to migrate as both are completely different chips. The SW for both the chips are also developed accordingly.