phy: Include NC-SI in phy setup

Add NC-SI to the usual phy handling. This makes two notable changes:
- Somewhat similar to a fixed phy, phy_connect() will create an NC-SI
phy if CONFIG_PHY_NCSI is defined.
- An early return is added to phy_read() and phy_write() to handle a
case like the NC-SI phy which does not define a bus.

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>

include/phy.h

@@ -15,6 +15,7 @@
 #include <linux/mii.h>
 #include <linux/ethtool.h>
 #include <linux/mdio.h>
+#include <log.h>
 #include <phy_interface.h>
 
 #define PHY_FIXED_ID		0xa5a55a5a
@@ -173,6 +174,11 @@ static inline int phy_read(struct phy_device *phydev, int devad, int regnum)
 {
 	struct mii_dev *bus = phydev->bus;
 
+	if (!bus || !bus->read) {
+		debug("%s: No bus configured\n", __func__);
+		return -1;
+	}
+
 	return bus->read(bus, phydev->addr, devad, regnum);
 }
 
@@ -181,6 +187,11 @@ static inline int phy_write(struct phy_device *phydev, int devad, int regnum,
 {
 	struct mii_dev *bus = phydev->bus;
 
+	if (!bus || !bus->read) {
+		debug("%s: No bus configured\n", __func__);
+		return -1;
+	}
+
 	return bus->write(bus, phydev->addr, devad, regnum, val);
 }
 
@@ -402,6 +413,7 @@ int phy_vitesse_init(void);
 int phy_xilinx_init(void);
 int phy_mscc_init(void);
 int phy_fixed_init(void);
+int phy_ncsi_init(void);
 int phy_xilinx_gmii2rgmii_init(void);
 
 int board_phy_config(struct phy_device *phydev);