+static int lan865x_set_hw_macaddr(struct net_device *netdev)
+{
+	u32 regval;
+	bool ret;
+	struct lan865x_priv *priv = netdev_priv(netdev);
+	const u8 *mac = netdev->dev_addr;
+
+	ret = oa_tc6_read_register(priv->tc6, LAN865X_MAC_NCR, &regval);
+	if (ret)
+		goto error_mac;
+	if ((regval & LAN865X_TXEN) | (regval & LAN865X_RXEN)) {

Would testing netif_running(netdev) be enough? That is a more common
test you see. In fact, you already have that in
lan865x_set_mac_address(). And in lan865x_probe() why would the
hardware be enabled?

+		if (netif_msg_drv(priv))
+			netdev_warn(netdev, "Hardware must be disabled for MAC setting\n");
+		return -EBUSY;
+	}
+	/* MAC address setting */
+	regval = (mac[3] << 24) | (mac[2] << 16) | (mac[1] << 8) | mac[0];
+	ret = oa_tc6_write_register(priv->tc6, LAN865X_MAC_SAB1, regval);
+	if (ret)
+		goto error_mac;
+
+	regval = (mac[5] << 8) | mac[4];
+	ret = oa_tc6_write_register(priv->tc6, LAN865X_MAC_SAT1, regval);
+	if (ret)
+		goto error_mac;
+
+	return 0;
+
+error_mac:
+	return -ENODEV;

oa_tc6_write_register() should return an error code, so return it.

+static int lan865x_set_mac_address(struct net_device *netdev, void *addr)
+{
+	struct sockaddr *address = addr;
+
+	if (netif_running(netdev))
+		return -EBUSY;
+
+	eth_hw_addr_set(netdev, address->sa_data);
+
+	return lan865x_set_hw_macaddr(netdev);

You should ideally only update the netdev MAC address, if you managed
to change the value in the hardware.

+static void lan865x_set_multicast_list(struct net_device *netdev)
+{
+	struct lan865x_priv *priv = netdev_priv(netdev);
+	u32 regval = 0;
+
+	if (netdev->flags & IFF_PROMISC) {
+		/* Enabling promiscuous mode */
+		regval |= MAC_PROMISCUOUS_MODE;
+		regval &= (~MAC_MULTICAST_MODE);
+		regval &= (~MAC_UNICAST_MODE);
+	} else if (netdev->flags & IFF_ALLMULTI) {
+		/* Enabling all multicast mode */
+		regval &= (~MAC_PROMISCUOUS_MODE);
+		regval |= MAC_MULTICAST_MODE;
+		regval &= (~MAC_UNICAST_MODE);
+	} else if (!netdev_mc_empty(netdev)) {
+		/* Enabling specific multicast addresses */
+		struct netdev_hw_addr *ha;
+		u32 hash_lo = 0;
+		u32 hash_hi = 0;
+
+		netdev_for_each_mc_addr(ha, netdev) {
+			u32 bit_num = lan865x_hash(ha->addr);
+			u32 mask = 1 << (bit_num & 0x1f);
+
+			if (bit_num & 0x20)
+				hash_hi |= mask;
+			else
+				hash_lo |= mask;
+		}
+		if (oa_tc6_write_register(priv->tc6, LAN865X_MAC_HRT, hash_hi)) {
+			if (netif_msg_timer(priv))
+				netdev_err(netdev, "Failed to write reg_hashh");
+			return;
+		}
+		if (oa_tc6_write_register(priv->tc6, LAN865X_MAC_HRB, hash_lo)) {
+			if (netif_msg_timer(priv))
+				netdev_err(netdev, "Failed to write reg_hashl");
+			return;
+		}
+		regval &= (~MAC_PROMISCUOUS_MODE);
+		regval &= (~MAC_MULTICAST_MODE);
+		regval |= MAC_UNICAST_MODE;
+	} else {
+		/* enabling local mac address only */
+		if (oa_tc6_write_register(priv->tc6, LAN865X_MAC_HRT, regval)) {
+			if (netif_msg_timer(priv))
+				netdev_err(netdev, "Failed to write reg_hashh");
+			return;
+		}
+		if (oa_tc6_write_register(priv->tc6, LAN865X_MAC_HRB, regval)) {
+			if (netif_msg_timer(priv))
+				netdev_err(netdev, "Failed to write reg_hashl");
+			return;
+		}
+	}
+	if (oa_tc6_write_register(priv->tc6, LAN865X_MAC_NCFGR, regval)) {
+		if (netif_msg_timer(priv))
+			netdev_err(netdev, "Failed to enable promiscuous mode");
+	}
+}

Another of those big functions which could be lots of simple functions
each doing one thing.

+/* Configures the number of bytes allocated to each buffer in the
+ * transmit/receive queue. LAN865x supports only 64 and 32 bytes cps and also 64
+ * is the default value. So it is enough to configure the queue buffer size only
+ * for 32 bytes. Generally cps can't be changed during run time and also it is
+ * configured in the device tree. The values for the Tx/Rx queue buffer size are
+ * taken from the LAN865x datasheet.
+ */

Its unclear why this needs to be a callback. Why not just set it after
oa_tc6_init() returns?

+static void lan865x_remove(struct spi_device *spi)
+{
+	struct lan865x_priv *priv = spi_get_drvdata(spi);
+
+	oa_tc6_exit(priv->tc6);
+	unregister_netdev(priv->netdev);

Is that the correct order? Seems like you should unregister the netdev
first.

+#ifdef CONFIG_ACPI
+static const struct acpi_device_id lan865x_acpi_ids[] = {
+	{ .id = "LAN865X",
+	},
+	{},

Does this work? You don't have access to the device tree properties.

     Andrew