Add error handling and exception scenarios

doc/smart-switch/reboot/reboot-hld.md

@@ -18,6 +18,7 @@
     - [NPU platform.json](#npu-platformjson)
     - [GNOI API implementation](#gnoi-api-implementation)
     - [reboot.py script modifications](#rebootpy-script-modifications)
+    - [Error handling and exception scenarios](#error-handling-and-exception-scenarios)
   - [Test plan](#test-plan)
 
 ## Revision ##
@@ -233,6 +234,14 @@ a complete switch reboot or targeting a specific DPU.
 * Add a new reboot_smartswitch() function to reboot either the entire switch or a particular DPU, which takes DPU ID as an argument that
 needs a reboot.
 
+### Error handling and exception scenarios ###
+
+* If the GNMI service is not operational on the DPU for any reason, detach the PCI, and proceed with the reboot after a timeout upon receiving an acknowledgment.
+
+* After the DPU reboots, if the DPU PCI fails to reconnect for any reason, an error-handling mechanism should be in place to restore the DPU.
+
+* In the event of power failure, a power-cycle due to a kernel panic, or any other unknown reason, both the DPU and NPU will undergo an ungraceful reboot.
+
 ## Test plan ##
 
 Presented below is the test plan within the ```sonic-mgmt``` framework for the smart switch reboot.