Corstone 1000 Cortex M0+


I have small query on this  --> here document says that bl1 is split into bl1_1 and bl1_2  -->  here the doc says there is only bl1.

So when i do git clone for TFM, there is bl1_1 and bl1_2 code, i am confused here, in the below link  looking at the diagram under secure boot chain

there is only bl1 and bl2.

So is it ok to use bl1 alone? How many bootloaders are present in cortex MO+?

Is it mandatory to use bl1_1 and bl1_2 as it is? Since we are dealing with ROM do we face any issues if we do not split the bl1 to bl1_1 and bl1_2?

Kindly please help me on this understanding Thanks a lot.