The gre interface cannot join the bridge through luci，why？

[ggsn]

My steps are as follows：
1.create gre-tap interface success by luci web interface
2.show interface in serial by ifconfig -a，gre4t-gt01 is created：

3.gre4t-gt01 is not found in the physical port list of the LAN on luci web interface，cannot add gre4t-gt01 to bridge br-lan，why？

this is configuration：
config interface 'lan'
option type 'bridge'
option proto 'static'
option ipaddr '192.168.1.1'
option netmask '255.255.255.0'
option ip6assign '60'
option ifname 'eth0.1 eth0.2'

config interface 'gt01'
option proto 'gretap'
option peeraddr '192.168.120.251'
option force_link '1'

how to change option ifname 'eth0.1 eth0.2' to option ifname 'eth0.1 eth0.2 gre4t-gt01' ?

BTW:Why add gre4t- as the prefix of the interface name

[trendy]

Tunneling interface protocols

You didn't add the network option.

@ggsn

BTW:Why add gre4t- as the prefix of the interface name

Most OpenWrt protocol handlers add a protocol-specific prefix to the UCI interface names. There is a default 15-character limit for interface names in the Linux kernel.
With prefixes seen at least as long as gre4t- and allowing possibility of using .VLAN notation, declared names should be kept under four (4) characters.
abcd.NNNN ⇒ gre4t-abcd.NNNN (15 characters)