Incidentally, for this DNS have custom-built records SRV. Theese records for Kerberos, for example:
$ dig _kerberos._tcp.host.com srv
;; QUESTION SECTION:
;_kerberos._tcp.host.com. IN SRV
;; ANSWER SECTION:
_kerberos._tcp.host.com. 3550 IN SRV 10 10 88 kerberos.host.com.
Requesting for any DNS-name SRV-record in this format, you can find the address of Kerberos-server for this domain. Similarly, we can do for Bitcoin by queryng about: "_bitcoin._tcp.host.com" or something.
All this is done covertly, human sees only the right part of the name: host.com
And for domain names with sub-domains Kerberos using TXT records to enable the customer to understand what realm it belongs to:
$ dig _kerberos.grid.host.com txt
;; QUESTION SECTION:
;_kerberos.grid.host.com. IN TXT
;; ANSWER SECTION:
_kerberos.grid.host.com. 3587 IN TXT "HOST.COM"
Bitcoin can use this for subdomains like www:
_bitcoin.www.host.com. 3587 IN TXT "HOST.COM"
i.e., human can send bitcoin to
www.host.com, bitcoin client check TXT _bitcoin.www.host.com for DNS-name of bitcoin "realm", than check SRV _bitcoin._tcp.host.com and, finally, sends bitcoins to IP, specified by this SRV-record.
This scheme is really a part of Kerberos standart and used, I think, more than 15 years.