dt-bindings: net: adi,adin: document LP Termination property

Add "adi,low-cmode-impedance" boolean property which, when present,
configures the PHY for the lowest common-mode impedance on the receive
pair for 100BASE-TX operation by clearing the B_100_ZPTM_EN_DIMRX bit.
This is suited for capacitive coupled applications and other
applications where there may be a path for high common-mode noise to
reach the PHY.

If this value is not present, the value of the bit by default is 1,
which is normal termination (zero-power termination) mode.

Signed-off-by: Osose Itua <osose.itua@savoirfairelinux.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Link: https://patch.msgid.link/20260107221913.1334157-2-osose.itua@savoirfairelinux.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/devicetree/bindings/net/adi,adin.yaml

@@ -52,6 +52,20 @@ properties:
     description: Enable 25MHz reference clock output on CLK25_REF pin.
     type: boolean
 
+  adi,low-cmode-impedance:
+    description: |
+      Configure PHY for the lowest common-mode impedance on the receive pair
+      for 100BASE-TX. This is suited for capacitive coupled applications and
+      other applications where there may be a path for high common-mode noise
+      to reach the PHY.
+      If not present, by default the PHY is configured for normal termination
+      (zero-power termination) mode.
+
+      Note: There is a trade-off of 12 mW increased power consumption with
+        the lowest common-mode impedance setting, but in all cases the
+        differential impedance is 100 ohms.
+    type: boolean
+
 unevaluatedProperties: false
 
 examples: