This pull request includes several changes to theETHClass in thelibraries/Ethernet/src/ETH.cpp andlibraries/Ethernet/src/ETH.h files. The changes primarily focus on adding support for configuring Ethernet settings such as full duplex mode, link speed, and auto-negotiation, as well as ensuring these settings are properly managed during the Ethernet initialization and shutdown processes.

Enhancements to Ethernet Configuration:

• Added new member variables_eth_started,_link_speed,_full_duplex, and_auto_negotiation to theETHClass to store Ethernet configuration settings.
• Implemented new methodssetFullDuplex,setLinkSpeed, andsetAutoNegotiation to allow configuration of Ethernet settings before callingETH.begin(). Each method includes validation to ensure settings are applied correctly.[1][2][3]
• Added private methods_setFullDuplex,_setLinkSpeed, and_setAutoNegotiation to apply the settings to the Ethernet hardware.

Initialization and Shutdown Process:

• Modified theETHClass::begin andETHClass::beginSPI methods to apply the Ethernet configuration settings (full duplex, link speed, and auto-negotiation) during the initialization process if auto-negotiation is disabled.[1][2]
• Updated theETHClass::end method to reset the_eth_started flag when shutting down the Ethernet interface.

Code Refactoring:

• Refactored theETHClass constructor to initialize the new member variables.
• Ensured that the_eth_started flag is set to true after successful initialization and set to false during shutdown.[1][2][3]

Reference:#10923