start mariadb but systemctl status mariadb with failed

I installed mariaDB under the path ‘/app/mysql’;

Since the configuration file could not be found, I created the 'my.cnf' file under the 'etc/mysql' path and copied the content online, my.cnf CODE:

[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock

log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid

When I run the command systemctl start mariadb, no error seems to be reported, but systemctl status mariadb says it failed. Code:

[root@iZbp13edmlpcdqu2759ccaZ system]# systemctl status mariadb
● mariadb.service - MariaDB - database server
   Loaded: loaded (/usr/lib/systemd/system/mariadb.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Thu 2023-10-19 20:31:46 CST; 13s ago
  Process: 115928 ExecStart=/app/mysql/bin/mysql -c /app/mysql (code=exited, status=1/FAILURE)
 Main PID: 115928 (code=exited, status=1/FAILURE)

Oct 19 20:31:46 iZbp13edmlpcdqu2759ccaZ systemd[1]: Started MariaDB - database server.
Oct 19 20:31:46 iZbp13edmlpcdqu2759ccaZ systemd[1]: mariadb.service: Main process exited, code=exited, status=1/FAILURE
Oct 19 20:31:46 iZbp13edmlpcdqu2759ccaZ systemd[1]: mariadb.service: Failed with result 'exit-code'.

mariadb.service code:

[Unit]
Description=MariaDB - database server
After=syslog.target
After=network.target

[Service]
Type=simple
User=mysql
Group=mysql


# ExecStartPre=/app/mysql/bin/mysql -t -c  /app/mysql

ExecStart=/app/mysql/bin/mysql -c  /app/mysql
ExecStop=/app/mysql/bin/mysql -s stop


PrivateTmp=true

[Install]
WantedBy=multi-user.target

I hope to start mariadb successfully. How should I modify it? Thanks for any help.