The phy-connection-type parameter is described in ePAPR 1.1:

Specifies interface type between the Ethernet device and a physical
layer (PHY) device. The value of this property is specific to the
implementation.
Signed-off-by: Madalin Bucur <madalin.bucur@oss.nxp.com>
Link: https://lore.kernel.org/r/1597917724-11127-1-git-send-email-madalin.bucur@oss.nxp.comSigned-off-by: Rob Herring <robh@kernel.org>