Hi,
Both DTB/DTS will be used. When booting, TF-A/uboot will use the TF-A DTS/DTB, when uboot passes the control to the kernel, the kernel will use its own DTB/DTS. There is no conflict between both.
Both DTB/DTS should be configured accordingly, if not when uboot passes control to the kernel, devices might not be available to the kernel itself.
Please, let us know.