[PATCH v3 3/3] Documentation: ABI: adl8113: add documentation

[Antoniu Miclaus <antoniu.miclaus@analog.com>]

Add ABI documentation for the ADL8113 Low Noise Amplifier,
covering the 4 pin-selectable operating modes.

Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
---

Changes in v3:
- Replace "mode" attribute documentation with "signal_path" attribute
- Update descriptions to reflect separation of gain control (hardwaregain) and path control (signal_path)
- Add explanation of automatic bypass mode switching when selecting external paths
- Update attribute names from mode/mode_available to signal_path/signal_path_available
- Clarify that external paths enable connection of external components for filtering or amplification
---
 .../testing/sysfs-bus-iio-amplifiers-adl8113  | 30 +++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-amplifiers-adl8113

diff --git a/Documentation/ABI/testing/sysfs-bus-iio-amplifiers-adl8113 b/Documentation/ABI/testing/sysfs-bus-iio-amplifiers-adl8113
new file mode 100644
index 000000000000..31fb1e6e80fc
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-iio-amplifiers-adl8113
@@ -0,0 +1,30 @@
+What:		/sys/bus/iio/devices/iio:deviceX/signal_path
+Date:		January 2025
+KernelVersion:	6.14
+Contact:	linux-iio@vger.kernel.org
+Description:
+		This attribute controls the signal routing path for the ADL8113
+		Low Noise Amplifier. The supported signal paths are:
+
+		* internal - Signal passes through internal path. Can be used with
+		  either amplifier mode (14dB gain) or bypass mode (0dB gain).
+
+		* external_a - Signal routes from RFIN to OUT_A and from IN_A to RFOUT
+		  (VA=0, VB=1). External components can be connected for filtering or
+		  additional amplification. Automatically switches to bypass mode (0dB).
+
+		* external_b - Signal routes from RFIN to OUT_B and from IN_B to RFOUT
+		  (VA=1, VB=0). External components can be connected for filtering or
+		  additional amplification. Automatically switches to bypass mode (0dB).
+
+		Note: Selecting an external path automatically sets the hardware gain
+		to 0dB (bypass mode) since external paths require bypass operation.
+
+What:		/sys/bus/iio/devices/iio:deviceX/signal_path_available
+Date:		January 2025
+KernelVersion:	6.14
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Reading this attribute returns a space-separated list of all
+		available signal paths for the ADL8113 device. The available paths
+		may depend on the current gain mode (hardwaregain setting).
-- 
2.43.0