net: mii_timestamper: check NULL in unregister_mii_timestamper()

Callers of unregister_mii_timestamper() currently check for NULL
value of mii_ts before calling it.

Place the NULL check inside unregister_mii_timestamper() and update
the callers accordingly.

Signed-off-by: Calvin Johnson <calvin.johnson@oss.nxp.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Acked-by: Grant Likely <grant.likely@arm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: mii_timestamper: fix static allocation by PHY driver

If phydev->mii_ts is set by the PHY driver, it will always be
overwritten in of_mdiobus_register_phy(). Fix it. Also make sure, that
the unregister() doesn't do anything if the mii_timestamper was provided by
the PHY driver.

Fixes: 1dca22b18421 ("net: mdio: of: Register discovered MII time stampers.")
Signed-off-by: Michael Walle <michael@walle.cc>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net: Add a layer for non-PHY MII time stamping drivers.

While PHY time stamping drivers can simply attach their interface
directly to the PHY instance, stand alone drivers require support in
order to manage their services. Non-PHY MII time stamping drivers
have a control interface over another bus like I2C, SPI, UART, or via
a memory mapped peripheral. The controller device will be associated
with one or more time stamping channels, each of which sits snoops in
on a MII bus.

This patch provides a glue layer that will enable time stamping
channels to find their controlling device.

Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>