Can you let me know the the following details of watchdog timer
What is the use of watchdog timer?
How it is configured?
How it is used in Software?
How to design the HW/RTL
I'm not sure if you are asking this question in general or specifically for Arm IP.Arm provides a watchdog timer IP:https://developer.arm.com/documentation/ddi0479/b/APB-Components/Watchdog
For general information on how and why to use a Watchdog, I recommend the below article (not written by Arm):https://interrupt.memfault.com/blog/firmware-watchdog-best-practices