Whenever i travel i take photos from both mobile phone as well as my DSLR. Later on i combine photos from both and select best photos. Problem is that because of different naming patterns in DSLR and mobile phone, the ordering of photos after combining is not as expected. I want photos of same place or photos taken at similar time to show up together. Any suggestions or solutions to achieve this?
The simplest answer is to use photo management software to do the work for you, rather than worry about file name conventions.
Applications such as Apple's Photos (especially if you're on an iPhone), Google's Photo management (if you're in the Google ecosystem), etc., make it trivial to manage your photos from multiple camera sources.
Edit: You state that you use Google Photos, but it doesn't help you to sort photos by date taken. From the Google Photos Help page, How do we sort photos by date taken?
The main Google Photos timeline/library view always sorts pictures by the date they were taken, with the most recent at the top. If you've uploaded pictures and they aren't in the correct date order, that means the EXIF metadata for those pictures does not contain the correct entry for Date Taken (or it doesn't contain a date at all).
This is, unfortunately, not uncommon when pictures are downloaded from certain other online sources or if they are edited with certain apps/software. Some cloud storage sites strip out a picture's original metadata when you download it, so there won't be a date in the Date Taken section of the EXIF metadata.
In those cases, when you upload the pictures to Google Photos, the only date that exists in the metadata is the date you downloaded it from that other site, or the date you made the edits. So, Google has no choice but to use that date for sorting.
You should check your downloaded pictures before uploading to Google Photos to make sure the dates are accurate. Most computer operating systems can display the more common EXIF details of a picture if you right-click and look at the Properties. Look for the Date Taken entry and see what's there. If it's incorrect, or if it's blank, then that picture will not be in the right place when you upload it. You'll have to manually adjust the date.
So make sure the date/time in your DSLR is set correctly, and however you get those photos into Google Photos, make sure that process doesn't strip the date and time EXIF data from those images.
If the date/time was set differently in each of the cameras, you can deal with it after the fact by batch operation. Just be sure to only change the images from one camera so that they match the other.
Ordering, or renaming, by timestamp is the obvious solution. But you have to take care to set the clock on your DSLR correctly, especially if you travel to different time zones and have your phone set to automatically obtain the network time.
There are various tools available to batch-change timestamps later, but that increases your workload, of course.
If you use Windows 10,
Right click start symbol (bottom left) and select 'File Explorer'.
Go to the folder that contains your photos.
There should be some tabs across the top of the page that say something like
Name Date modified Type Size
Right click to the right of Size
One of the options should be 'Date Created'
Select this to add a new tab
Click on the tab Date Created.
This should order ALL the files in this folder by their creation date i.e the date they were taken