Add manual test case for DMIC capture

test-case/manual/check-DMIC-capture-2ch-4ch.md

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+# Check DMIC 2ch/4ch
+
+Verification of 2ch/4ch DMIC recording 
+
+## Preconditions
+1. The system is powered on.
+2. A Linux-based system with with PCH DMIC connected, ex:"Realtek AIOC and transducer card"
+
+## Note
+* This is specifically to test recording with PCH-connected DMIC
+
+
+## Test Description
+* Verification of 2ch/4ch DMIC recording 
+* Recording should happen without any issue
+* Playback should be smooth without any glitches or noise.
+
+## Recording via 2ch/4ch DMIC
+1. Verify dmic device list.
+   ```bash
+    arecord -l
+    ```
+2. Capture audio using dmic device:
+    ```bash
+    arecord -Dhw:0,0 -c 2 -r 48000 -f S24_LE -d 20 test.wav -vvv for 2Ch
+    arecord -Dhw:0,6 -c 4 -r 48000 -f S32_LE -d 15 test3.wav -vvv for 4ch
+    ```
+3. Play and verify the audio file recorded in step 3:
+    ```bash
+    aplay -Dhw:0,0 -c 2 -r 48000 -f S24_LE test.wav -vvv 
+    ```
+   Note : 4ch dmic recording copy in IT laptop and play & verify 
+    ```
+4. Check the dmesg log:
+    ```bash
+    dmesg | grep -E "snd|sof|soc" | grep -i error
+    ```
+
+
+## Expected Results
+1. DMIC devices should list
+2. Audio capture should happen without any issues
+3. Playback should be smooth without any glitch
+4. No audio errors or failures should be present in the dmesg log.
+