A zone for the reverse resolve (PTR) is treated the same way as a zone for a normal domain.

An Example for the reverse zone of the IP net:   192.168.1.0/24

The zone is called:   1.168.192.in-addr.arpa

$TTL 86400      ; 1 day
1.168.192.in-addr.arpa.   IN      SOA     ns1.dnsserver.de. root.ns1.dnsserver.de. (
YYYYMMDD01 ; serial
10800      ; refresh (3 hours)
3600       ; retry (1 hour)
604800     ; expire (1 week)
604800     ; minimum (1 week)
)
IN      NS      ns1.dnsserver.tld
IN      NS      ns2.dnsserver.tld

1            IN      PTR     reverse.name1.tld
2            IN      PTR     reverse.name2.tld
3            IN      PTR     reverse.name3.tld