How to disable or remove ethernet in openwrt?

I’m using vocore2, and present the boot time of my vocore2 running OpenWrt 19.07.3 is 30seconds, I want to decrease it by 10 seconds, while going through dmesg log I found starting ethernet takes around 7sec, so disabling ethernet will decrease boottime by 7sec.

[   15.022570] kmodloader: done loading kernel modules from /etc/modules.d/*
[   22.710060] br-lan: port 1(eth0.1) entered blocking state
[   22.715623] br-lan: port 1(eth0.1) entered disabled state
[   22.721459] device eth0.1 entered promiscuous mode
[   22.726517] device eth0 entered promiscuous mode
[   22.751465] br-lan: port 1(eth0.1) entered blocking state
[   22.757014] br-lan: port 1(eth0.1) entered forwarding state
[   22.762876] IPv6: ADDRCONF(NETDEV_UP): br-lan: link is not ready
[   23.722126] efuse_probe: efuse = 10000012
[   23.899450] tssi_1_target_pwr_g_band = 25
[   29.820162] <==== rt28xx_init, Status=0
[   29.844215] IPv6: ADDRCONF(NETDEV_CHANGE): br-lan: link becomes ready
[   32.083358] br-lan: port 2(ra0) entered blocking state
[   32.088656] br-lan: port 2(ra0) entered disabled state
[   32.094226] device ra0 entered promiscuous mode
[   32.098903] br-lan: port 2(ra0) entered blocking state
[   32.104169] br-lan: port 2(ra0) entered forwarding state

So how to remove ethernet in openwrt?