Add dap8211r_write_ext() to write extended registers via the indirect
access registers of the phy.

This will be used to write extended registers of the dap8211r.

No functional change.

Signed-off-by: Artem Shimko <a.shimko.dev@gmail.com>
---
 drivers/net/phy/dap8211r.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/net/phy/dap8211r.c b/drivers/net/phy/dap8211r.c
index 0bf770f8ebbb..4eb50c26397f 100644
--- a/drivers/net/phy/dap8211r.c
+++ b/drivers/net/phy/dap8211r.c
@@ -88,6 +88,32 @@ static int dap8211r_read_ext(struct phy_device *phydev, u16 reg)
 	return ret;
 }
 
+/**
+ * dap8211r_write_ext() - Write extended register
+ * @phydev: PHY device structure
+ * @reg: Extended register address
+ * @data: Data to write
+ *
+ * Writes a PHY extended register using the indirect access method.
+ * The caller must hold the MDIO bus lock.
+ *
+ * Return: 0 on success, or negative error code
+ */
+static int dap8211r_write_ext(struct phy_device *phydev, u16 reg, u16 data)
+{
+	int ret;
+
+	phy_lock_mdio_bus(phydev);
+	ret = __phy_write(phydev, DAP8211R_EXT_ADD, reg);
+	if (ret < 0)
+		goto out;
+
+	ret = __phy_write(phydev, DAP8211R_EXT_DATA, data);
+out:
+	phy_unlock_mdio_bus(phydev);
+	return ret;
+}
+
 /**
  * dap8211r_modify_ext() - Modify extended register bits
  * @phydev: PHY device structure
-- 
2.43.0