We need a Ethernet switch whose RGMII interfaces are able to operate at 3.3V. The IEEE802.3 standard specifies 2.5 voltage levels for RGMII but all PHYs that I found so far also support 3.3V.
The SJA1105 would fit very well in our application but we are unsure wether it supports RGMII with 3.3V voltage level.
While the SJA1105P datasheet https://www.nxp.com/docs/en/data-sheet/SJA1105PQRS_SDS.pdf page 3 specifies 3.3V for MII, RMII and RGMII for the SJA1105, the SJA1105 datasheet https://www.nxp.com/docs/en/data-sheet/SJA1105.pdf specifies 2.5V on page 16.
My guess (and my hope) is that NXP just repeats the standard's values in the SJA1105 datasheet, while it is still possible to operate it's RGMII at 3.3V.
Can anybody please confirm that the SJA1105 supports 3.3V voltage levels also in RGMII mode?
You correctly noticed that the SJA1105/T data sheet specifies RGMII operations at 2.5V voltage level only. The SJA1105P/Q provides extended capabilities and support RGMII at 1.8V/2.5V/3.3V levels. Using the SJA1105 out of the specification as you wish is not what NXP can recommend, however most probably it will work.