Removing myself as assignee as I really have no idea right of the bat what we are after here and I will most likely not have the time to dig into all the gory details.

Here is the doc for what is supported w.r.t. configuration in dracut for these types of situation:

http://man7.org/linux/man-pages/man7/dracut.cmdline.7.html

and in detail the way the network would be configured:

ip={dhcp|on|any|dhcp6|auto6|either6}

           dhcp|on|any
               get ip from dhcp server from all interfaces. If root=dhcp,
               loop sequentially through all interfaces (eth0, eth1, ...)
               and use the first with a valid DHCP root-path.

           auto6
               IPv6 autoconfiguration

           dhcp6
               IPv6 DHCP

           either6
               if auto6 fails, then dhcp6

       ip=<interface>:{dhcp|on|any|dhcp6|auto6}[:[<mtu>][:<macaddr>]]
           This parameter can be specified multiple times.

           dhcp|on|any|dhcp6
               get ip from dhcp server on a specific interface

           auto6
               do IPv6 autoconfiguration

           <macaddr>
               optionally set <macaddr> on the <interface>. This cannot be
               used in conjunction with the ifname argument for the same
               <interface>.

       ip=<client-IP>:[<peer>]:<gateway-IP>:<netmask>:<client_hostname>:<interface>:{none|off|dhcp|on|any|dhcp6|auto6|ibft}[:[<mtu>][:<macaddr>]]
           explicit network configuration. If you want do define a IPv6
           address, put it in brackets (e.g. [2001:DB8::1]). This parameter
           can be specified multiple times.  <peer> is optional and is the
           address of the remote endpoint for pointopoint interfaces and it
           may be followed by a slash and a decimal number, encoding the
           network prefix length.

           <macaddr>
               optionally set <macaddr> on the <interface>. This cannot be
               used in conjunction with the ifname argument for the same
               <interface>.

       ip=<client-IP>:[<peer>]:<gateway-IP>:<netmask>:<client_hostname>:<interface>:{none|off|dhcp|on|any|dhcp6|auto6|ibft}[:[<dns1>][:<dns2>]]
           explicit network configuration. If you want do define a IPv6
           address, put it in brackets (e.g. [2001:DB8::1]). This parameter
           can be specified multiple times.  <peer> is optional and is the
           address of the remote endpoint for pointopoint interfaces and it
           may be followed by a slash and a decimal number, encoding the
           network prefix length.

ifname=<interface>:<MAC>
           Assign network device name <interface> (i.e. "bootnet") to the
           NIC with MAC <MAC>.

               Warning
               Do not use the default kernel naming scheme for the interface
               name, as it can conflict with the kernel names. So, don’t use
               "eth[0-9]+" for the interface name. Better name it "bootnet"
               or "bluesocket".

       rd.route=<net>/<netmask>:<gateway>[:<interface>]
           Add a static route with route options, which are separated by a
           colon. IPv6 addresses have to be put in brackets.

           Example.

                   rd.route=192.168.200.0/24:192.168.100.222:ens10
                   rd.route=192.168.200.0/24:192.168.100.222
                   rd.route=192.168.200.0/24::ens10
                   rd.route=[2001:DB8:3::/8]:[2001:DB8:2::1]:ens10

       bootdev=<interface>
           specify network interface to use routing and netroot information
           from. Required if multiple ip= lines are used.

       nameserver=<IP> [nameserver=<IP> ...]
           specify nameserver(s) to use

Then there are vlan, bond, bridge, and team kernel command line arguments one could use.