Connections between Domain, Nginx and Wordpress - wordpress

Question

I want to understand the connections between Nginx Config Files, Domains and Wordpress Site URL.
I map my domain blog.example.com to my ip: xxx.xxx.xxx.xxx/wordpress/
in the Wordpress SiteUrl i set blog.example.com
How should my NGINX configuration file look like?
Edit
My Configuration works in the first step, I get to the Frontpage, but when clicking on permalinks, I get redirected to the Frontpage again instead of the Post.
My current Config looks like this:
server {
listen 80 default_server;
root /var/www/wordpress/;
index index.html index.htm index.php
server_name blog.example.com;
location ~\.php$ {
try_files $uri =404;
fastcgi_pass php:9000;
fastcgi_index index.php;
include fastcgi_params;
fastcgi_param SCRIPT_FILENAME $request_filename;
fastcgi_param REQUEST_URI $uri?$args;
}
location / {
try_files $uri /index.php$args;
}
}
Edit
In Nginx Debug Log I see the REQUEST_URI is /wordpress/postname/
but as i understand it should be just /postname/

Answer 1

How about this:
server {
listen 80;
server_name _;
return 404; # default
}
server {
listen 80;
server_name blog.example.com;
location / {
return 301 http://blog.example.com/wordpress;
}
location ^~ /wordpress {
proxy_set_header X-Forwarded-Host $host;
proxy_set_header X-Forwarded-Server $host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_pass http://xxx.xxx.xxx.xxx;
}
}