I given all 4 round but then NVIDIA ghostted me never heard back from HR . Process took around 1.5 months.
Note : 2,3,4 th round were scheduled on same day.
(Ignore speliing mistakes)

Following are all the qustions they asked me through out the rounds

1st Round

Basic C qustions, Static , volatile, then Discuss one use of BLE (my previous work related to bluetooth low energy like how can we design BLE based key using callibaration of singnals)

2nd, 3rd, 4th round qustions are listed below

Check endieness of by array
Access the Adress through string
Reverse string
Implement Malloc and implement printf
Explain how ping works and explain osi model and explain how header are added
Implment ping
Pointer arithmetic on 2 d array
Middle node in linked list
Volatile
Const
All major os concepts in brief
Storage classes
Call by value and reference
Linux drivers explanation basics
ISR handling
Spinlocks
Process synchronisation techniques
Given 2 arrays merged them to sort or write a sort function
Discussion about projects
Paging
Context switching