Thank you for asking about Intel® Ethernet controllers. I am not a design expert, but in discussing this question with our engineering team they came up with the following suggestions using the Intel® 82580 Gigabit Ethernet Controller.
82580 <-- SERDES and MDIO(SMI) --> Marvell 88e6092 (or any switch with 1G SERDES support)
82580 <-- SGMII and MDIO(SMI) --> Marvell 88e1111 <-- MII (and MDIO from 82580) --> Marvell 88E6083
These solutions might work. Intel has not validated these solutions and does not provide drivers to control the MDIO(SMI) interface on the switch.
The Intel 82580 Gigabit Ethernet Controller is not sold as an IT part so you would need to do your own industrial temperature cold testing for it. We don’t offer an MDIO + Industrial Temperature solution.
The Intel® 82574IT Gigabit Ethernet Controller is tested for Industrial Temperature, but it doesn’t offer MDIO.