In case a PHY supports only one LED in total, like ADIN1300, and this LED
is described in DT, it is currently necessary to include unit address in
the LED node name and the address-cells have to be set to 1:

leds {
  #address-cells = <1>;
  ...
  led@0 {
    reg = <0>;
    ...
  };
};

For a single LED PHY, this should not be necessary and plain 'led' node
without unit should be acceptable as well:

leds {
  ...
  led {
    ...
  };
};

Handle this special case. In case reg property is not present in the leds
node subnode, test whether the leds node contains exactly one subnode, and
if so, assume this is the one single LED with reg property set to 0.

Signed-off-by: Marek Vasut <marex@denx.de>
---
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Heiner Kallweit <hkallweit1@gmail.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: netdev@vger.kernel.org
---
 drivers/net/phy/phy_device.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 5b34d39d1d52a..fa91d03d9e920 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c

@@ -3346,6 +3346,7 @@ static int of_phy_led(struct phy_device *phydev,
 	struct led_classdev *cdev;
 	unsigned long modes = 0;
 	struct phy_led *phyled;
+	int led_count;
 	u32 index;
 	int err;
 

@@ -3357,8 +3358,18 @@ static int of_phy_led(struct phy_device *phydev,
 	phyled->phydev = phydev;
 
 	err = of_property_read_u32(led, "reg", &index);
-	if (err)
-		return err;
+	if (err) {
+		led_count = of_get_available_child_count(of_get_parent(led));
+
+		/*
+		 * If there is one PHY LED in total, accept 'led' subnode
+		 * in addition to 'led@0' subnode, and assume reg = <0>;
+		 */
+		if (total_led_count != 1)
+			return err;
+		index = 0;
+		err = 0;
+	}
 	if (index > U8_MAX)
 		return -EINVAL;
 

-- 
2.45.2